Chapter Three.

Chapter Three.The Seven Dots.In a cosy little house at Veneux Nadon, near Moret-sur-Loing, in the great Forest of Fontainebleau, Dick, Yvette, and Jules were seated in earnest conversation. They made a remarkable trio. Dick was unmistakably English, Yvette and her brother as unmistakably French—the girl dark-haired and dark-eyed, and with all the grace and vivacity which distinguish Frenchwomen of the better class. Her brother, quiet and dreamy, lacked his sister’s vivacity, but there was a suggestion of strength and iron resolution in the firm mouth and steely eyes.“It will be terribly dangerous, Dick,” said Yvette, with an altogether new note of anxiety in her voice.“I suppose it will,” replied Dick, “but,”—and his voice hardened as he spoke—“I don’t see what else we can do. We cannot run the risk of seeing a perfected helicopter in German hands. It would be too fearful a weapon. We must get hold of the plans and destroy the machine, whatever the risk may be.”Strange stories had come through the French Secret Service of a new and wonderful type of aircraft which was being tested with the utmost secrecy somewhere in the neighbourhood of Spandau, the great military town near Berlin. Of its precise character little was known or could be ascertained, and even Regnier, the astute and energetic head of the French Secret Service, had at length to confess himself utterly beaten. His cleverest agents had been baffled; more than one was in a German prison, with little hope of an early release. In the meantime the mysterious machine flitted about the neighbourhood of the great garrison, always at night, appearing and disappearing under circumstances which proved conclusively that it must be of a type which differed widely from any yet known to the public.“We must go, Dick,” said Yvette, “and Regnier is extremely anxious that you should help us. His trouble is that while he has dozens of capable men at his command none of them has a really expert knowledge of aviation. He thinks that if you once got a good look at the machine you could form a complete idea of what it really is.”“Very well,” said Dick, “we will look upon it as settled. We must work out a plan.”For many months Dick Manton had been working steadily and secretly at Veneux Nadon under the auspices, though not actually in the employ, of the French Secret Service. He had offered the plans of the Mohawk to the British War Office, only to be met with a reception so chilly as effectually to discourage him from proceeding further in the matter. Regnier, however, was a man of a different stamp from the British bureaucrat—keen as mustard and with the saving touch of imagination which is characteristic of the best type of Frenchman. He had unbounded faith in Yvette, who had for some time been one of his most trusted lieutenants, and when, angry at the attitude of the British War Office, she had given him a hint of what the Mohawk could really do, he had offered Dick the fullest facilities for continuing his work. Under the circumstances Dick had felt that to refuse would have been absurd.Veneux Nadon was a lonely little spot. Here Dick, though only thirty miles from Paris, found himself in complete seclusion, with a well-equipped workshop in large grounds completely buried in the lovely forest, and thoroughly screened from prying eyes. Regnier had put the matter to him quite plainly.“You are an Englishman, Monsieur Manton,” he had said, “and I will not ask you to sell your secret to France. But we are willing to bear the expense of perfecting your invention on the distinct understanding that when the time comes England shall have the option of sharing in it to the exclusion of all other countries except France. When you are ready we will officially invite the British Government to send a representative and will give them the opinion of coming in on equal terms. I do not think we can do more or less.”So it was settled, and for many months Dick and Jules had toiled on the building of a new Mohawk whose performances far surpassed those of the machine lost in the Adriatic. It was now completed and its preliminary tests had satisfied them that they had forged a weapon of tremendous potency.The machine was of the helicopter type. The idea, of course, was not new, but Dick had solved a problem which for many years had baffled inventors whose dream it was to construct a machine which should have the power of rising vertically from the ground and remaining stationary in the air.Driven upward by powerful propellers placed horizontally underneath the body, the Mohawk was capable of rising from the ground at a tremendous speed. Once in the air the lifting propellers were shut off and the machine moved forward under the impulse of the driving screws placed in the front and rear. These screws were the secret of Dick Manton’s triumph. They were of a new design, giving a tremendous ratio of efficiency. In size they wore relatively tiny, but possessed far greater power than any propeller known. The machine itself was nearly square. The body was completely covered by the big, single plane, measuring about twenty feet each way. This was the outside size of the machine and so perfectly was the helicopter controlled that Dick had repeatedly brought it to earth in a marked space not more than thirty-two feet square.Fitted with the new silencer which Dick had discovered and applied to the old Mohawk with such signal success, the engine was practically noiseless. At high speed the tiny propellers emitted only a thin, wailing note, barely audible a few yards away. Time and again Dick had sailed on dark nights only a few feet above the house roofs of Paris and had found that the noise of the ordinary traffic was amply sufficient to prevent his presence being discovered.To ensure absolute secrecy the various parts of the machine had been made in widely separated districts of France, and had been brought from Paris to Veneux Nadon, where Dick and Jules had carried out the erection of the machine alone. The very existence of the new aeroplane was utterly unsuspected by the few villagers who lived in the neighbourhood.Keenly interested in his work Dick had thoroughly enjoyed the peaceful life in the depths of the beautiful forest. He and Jules had become the closest of friends, and with Yvette, whose winning personality seemed to bind him to her more closely day by day, they made up a happy house party. They were looked after by a capable old peasant woman who was the devoted slave of all three, but whose admiration for Yvette seemed to rise almost to the point of veneration.On the day following the conversation recorded above, they were surprised to receive a visit from Regnier himself—an alert, dark-eyed man who seemed seriously perturbed.“There is no time to be lost,” he declared. “I hear to-day from Gaston that he has managed to get a near view of the new German machine. He says it rose apparently from the flat roof of a house standing in its own grounds outside Spandau. He happened to be near and caught sight of it just in time. Of course it was dark and he could see no details. But he is positive that the machine rose nearly straight up from the flat roof at an angle far too steep for any of our machines. That alone is sufficient to show that the Germans have got hold of something new and valuable. He waited for a long time, and finally saw the machine return. He declares it landed again on the roof. Evidently, Monsieur Manton, they have found out something along the lines of your invention, even if they have not actually got your secret.”“How far away was Gaston when he saw it?” asked Dick.“It must have been at least a quarter of a mile,” replied Regnier, “as the grounds are very extensive. Gaston dared not venture an attempt to get inside; the high fence is utterly unscalable, and the two lodge gates are always kept locked and there is a keeper at each.”“And he heard the engine?”“Yes, he says so specifically,” replied the Chief.“Well,” said Dick, “at any rate we are ahead of them to that extent. If it had been my machine he would not have heard the engine at all at that distance.”“However,” he went on, “it is evidently time we acted. Now, Monsieur Regnier, Mademoiselle Pasquet has told me what you want. I am willing to go. But I shall have to take the Mohawk. How are we to hide it? I can get over and back at night safely enough, but to hide the machine in the day-time will be another matter.”“Gaston can arrange that,” the Chief declared. “You know he has a farm a short distance outside, Spandau. There is a big barn there with no sides, and your machine can be easily dragged into it and concealed during the day. You know Gaston is passing as a German farmer. He has acted for years for us in this way and has never even been suspected. But you could not stay long.”“Very good,” said Dick. “I think the best plan will be for Jules to go by motor and for Mademoiselle to go separately by train. They must find out somehow exactly where the German plane is lodged and, if possible, where the plans are likely to be kept, and I must act accordingly. In any case, there will be no difficulty in smashing up the machine, but unless we destroy the plans as well they will be building another too soon to suit us. I will go to Verdun and wait there with the Mohawk until the time comes for me to fly over.”Jules and Yvette left the next day. Jules’ car was quite an ordinary one, but it had one important detail added. In the hollow flooring was cunningly concealed a small but powerful wireless telegraph set, the power for which was supplied by the engine. It was highly efficient, but had one serious drawback; it could only be used while the car was at rest owing to the necessity for running an aerial wire up some tall structure, such as a building or a tree. This, in a country where every one was specially suspicious of spies, was a serious peril.Three days later seven mysterious dots began to excite the ungovernable curiosity of the wireless world!Jules and Yvette, on arrival in Berlin, had taken rooms adjoining one another at the “Adlon,” the big cosmopolitan hotel which is always crowded with visitors from every country under the sun. Yvette posed as a school teacher on an educational tour, but her position was one of great danger. It was impossible to disguise her face, and although she had done what she could to destroy her French individuality by wearing peculiarly hideous German clothes, there was the ever-present danger that she would be seen and recognised by some of the many German agents who during the war had learnt to know her features, and who had good reason to remember her daring exploits in Alsace.At the same time, in order to have a possible retreat in a humbler neighbourhood, Yvette had hired a room in one of the mean quarters of the town, putting in a few miserable sticks of furniture and giving out that she was a sempstress employed at one of the big shops.She and Jules had decided never to speak in public. It was essential, however, that they should be able to communicate freely, and through the wall between their rooms Jules had bored with a tiny drill a hole through which he had passed a wire of a small pocket telephone. They could thus talk with ease and with the doors of their rooms locked they were absolutely safe from detection so long as they spoke in a whisper.It was on a dark night, the sky obscured by heavy masses of clouds, that Dick rose in the Mohawk from the Forest of Fontainebleau and headed for Verdun. A couple of hours’ flying brought him over the fortress and he descended in a clearing in a dense wood where he was welcomed by Captain Le Couteur, the chief engineer of the military wireless station. Covered with big tarpaulins, the Mohawk was left under the guard of a dozen Zouaves, and Dick and Captain Le Couteur motored to the citadel.Here the Captain took Dick directly into the steel-walled chamber deep under the fortifications which was the brain of the defences of Verdun. It was the nucleus of the entire system of telegraph and telephone wires which, in time of war, would keep the commander of the troops in the district fully informed of everything that was happening in every sector of the defences. The innermost room of all, where none but the Captain himself had access, contained the secret codes which dozens of foreign agents would have willingly risked their lives to possess. Their efforts—and they knew it—would have been in vain, for the chamber was guarded day and night by a band of picked men whose fidelity to France was utterly beyond the possibility of suspicion.“Your messages have already started—the seven dots at intervals of seven seconds,” said Captain Le Couteur when they were comfortably seated in the innermost room. “I got half a dozen test calls last night and everything seems to be working well. I expect they are arousing some interest, for operators all over Europe will be mystified. There will be another call about nine o’clock and in the meantime you had better get some sleep. I will call you if anything happens.”Dick stretched himself on a couch and slept peacefully. Nine o’clock found him with Captain Le Couteur seated in the innermost room at a table covered with delicate wireless apparatus. Turning a switch, the Captain lit up the row of little valves, put the receiving set in operation, and assuming one headpiece himself, handed another to Dick.He placed his hand upon one of the ebonite knobs of the complicated apparatus and slowly turned it. Then he turned a second condenser very carefully.“We are on the ordinary six-hundred-metre wave-length now,” the Captain explained, “and shall remain so until we get our seven dots. I am bound to keep the machine so or I should miss other messages I ought to hear. But we will change as soon as we get your signal.”Presently they came, sharp and clear, dot-dot-dot-dot-dot-dot-dot. Immediately Captain Le Couteur made some swift adjustments.“Now listen,” he said, “we are on a three-hundred-and-fifty-metre wave-length.”A moment later came three M’s—three pairs of dashes.“That’s Code Five,” said Captain Le Couteur. “Now we shall get the real message.”It came in what to Dick was a gibberish of letters and figures, but Captain le Couteur wrote it down and then, decoding it, read it off with the skill of the expert. It ran:“M M M begins Have located the machine stop Apparently entirely new type stop Tell Manton to be ready stop M M M ends.”“That’s our newest code,” the Captain explained, “and this is the first time it has been used. Jules learnt it only just before he left. It is very unlikely that the message has been picked up by anyone else, as the wave-length is quite low, but even if it was, no one could decipher the code from such a short message. They would want one very much longer, and even then it would probably take at least a week or ten days of very hard work by a lot of experts.”And he paused.“I think it would be well now for one of us to be constantly here,” he went on. “Perhaps, too, you would like to overhaul your machine so as to have it absolutely ready to get away at a moment’s notice. My fellows will give you any help you want and they are all absolutely to be depended upon not to talk.”Dick soon had the Mohawk ready; indeed there was not much to do after such a short trip as the flight to Verdun. The rest of the day he spent chatting with Captain Le Couteur, finding him a delightful companion and full of enthusiasm on the subject of wireless, of which his knowledge seemed boundless. Dick felt he could never tire of admiring the wonderfully ingenious devices which the other had invented and put into operation in his underground fortress.Several more messages, chiefly brief reports, were received from Jules, always heralded by the seven dots and begun with the three M’s which signified the secret code number Five. For a few hours everything seemed to be going well. Then, towards evening came graver news, which on being deciphered, read:“M M M begins Much fear Yvette suspected stop Tell Manton to be ready instant action stop M M M ends.”It could only mean, they realised, that Yvette had been recognised by a German agent and was being closely watched. The position was dangerous.Dick spent the next few hours in an agony of suspense. But he could do nothing. His first instinct was to fly to Berlin. But Le Couteur’s iron common-sense showed him clearly enough that to do so would be futile. To keep the Mohawk in Germany, even for a single day, would be risky; to try to hide her there for perhaps a week till they got a chance to rescue Yvette would be suicidal.A sudden swoop, swift and relentless action, and a quick escape were the essentials of success.Captain Le Couteur was scarcely less anxious than Dick himself. He had known Yvette since she was a child; they came from the same town in Alsace. But he possessed a brain of ice and restrained Dick’s impetuosity, though guessing shrewdly at its cause.“The time is not come yet,” he declared. “This is a bit of business which must go to the last tick of the dock. Mademoiselle herself would never forgive us if we spoilt everything by undue precipitation, and, after all, Monsieur Manton, France is of even more importance than Mademoiselle Pasquet, much as I admire her.”“I know,” Dick admitted. “But when I think of her, with her war record, which they know all about, falling into the hands of those brutes, I can hardly sit still.”“They have not got her yet and she is very clever,” replied Le Couteur. “Let us hope that she will give them the slip.”But about ten o’clock the following morning the dreaded blow fell.They were seated in the underground chamber, Dick ill at ease and full of gloomy forebodings. The apparatus set to receive messages on three-hundred-and-fifty-metres. Suddenly a buzzing noise was emitted from the loud-speaking telephone on the bench.Seven dots, seven times repeated, clicked out strong and dear!Surely seconds had never passed so slowly! It seemed an age before Captain Le Couteur, his face white as chalk, took down the message which followed, and then referring to the code, read:“Yvette arrested this morning by Kranzler.”Dick turned dizzy and the room spun round him as the dreadful significance of the words struck him. Kranzler, of all men! The murderer of Yvette’s father and mother, the man whom she had beaten over and over again at his own game of espionage during the war, the man whose sensational attempt to dispose of Rasputin’s stolen jewels had been foiled by Yvette’s skill and daring! He was, as they knew, a desperate brute who would stick at nothing to feed his revenge.Dick was rushing from the room, determined at all hazards to leave for Berlin at once, when Le Couteur seized his arm in a grip of iron.“Steady, Manton,” he said sharply. “Don’t be a fool. You’ll spoil everything. Sit down and wait for more news.”The words brought Dick to his senses.“I’m sorry, Le Couteur,” he said, “but I think I went a bit mad. You are quite right. But Kranzler—of all men! You know the story, of course?”Le Couteur nodded.“It could hardly be worse,” he admitted, “and there’s no use disguising the fact. But we must wait for more from Jules. In the meantime I am going to talk to Regnier. He must have more men on the spot. At all costs Mademoiselle must be rescued.”They were soon in touch with the Chief in Paris, who was horrified at the news.“I will get some more men over at once,” he said. “But we can do nothing until we find out where they have taken her. Jules will realise that. You are certain to get another message from him before long.”It was not until later that day that they learned how the arrest had been effected. Yvette, as soon as the position of the German plane had been located, had managed in the guise of a girl seeking work, to scrape acquaintance with one of the maids employed at the big house where the aeroplane was lodged. The girl had actually taken her up to the house and Yvette had coolly applied to the housekeeper for employment. There was, as it happened, no vacancy, but Yvette had used her eyes to good purpose. In the walk from the lodge to the house and back she had caught sight of the shed in which, obviously, the aeroplane was housed, and had noted its exact position in the extensive grounds. Hurrying back to the hotel she had communicated this information to Jules and both were filled with excitement at the important step forward they had made.Sitting in the lounge of the “Adlon” next morning Jules had seen Kranzler enter. He had started at once to warn Yvette to “lie low,” but was just too late. Yvette at that moment came down the staircase and before Jules could interpose had met Kranzler face to face. She was instantly recognised.With a grin of delight on his evil face the big German bowed profoundly.“This is indeed a pleasure, Mademoiselle Pasquet!” he said ironically.Yvette very coolly tried to carry it off.“Monsieur has, I think, made a mistake,” she said in German.“It’s no use, Mademoiselle,” was the harsh reply, “I know you perfectly. You must come with me—or shall I call the police?”There was obviously nothing for it but to obey, and Yvette was forced to leave the hotel in the clutches of the one man in all Germany she had the greatest reason to fear.Jules acted promptly. Slipping out of the hotel he hurriedly wheeled to the front a motor-bicycle he had hired to enable him to travel speedily between Berlin and Spandau. He got round just in time to see Kranzler put Yvette into a taxi, and followed them until they alighted at the door of the house in the Koeniggratzer-strasse which was the head-quarters of the German Secret Service. Yvette was taken inside.To get the news to Dick was now Jules’ first consideration. Knowing something of the methods of the German Secret Service he was reasonably sure that Yvette would be put through a long examination before she was taken to prison, and he decided to run the risk of being absent for a short time to get his message away. He drove hastily in his car out into the country until he found a tree to which his aerial wire could be attached and got off the brief message which conveyed the news to Verdun. Then he returned to watch, and ascertain where Yvette was to be imprisoned.The taxi was still outside the door when he got back to the Koeniggratzer-strasse. As an excuse for waiting he feigned engine trouble and tinkered with his machine, keeping all the time a close watch on the door opposite.He had not long to wait. In about half an hour Yvette was brought out, still in the custody of Kranzler, and driven away. Jules followed, and, at length, had the satisfaction of knowing that Yvette was in the big prison outside Spandau. It was a melancholy satisfaction, it is true, but to know where she was was of supreme importance.Driving to Gaston’s farm he soon informed Verdun where Yvette was located and then turned to discuss the position with Gaston.To his intense surprise and delight, Gaston was able to give him some comfort.“Of course, it is a great misfortune,” he said, “but it might be worse. They have taken her to the one prison in Germany where we have been able to keep a thoroughly trustworthy agent. He is a warder who passes as Herman Fuchs; his real name is Pierre Latour. We shall soon know all about Mademoiselle.”The front of the prison was in dear view from Gaston’s farm. Going outside, he called on Jules to help him to move one of three large barrels, each containing a big flowering shrub, which stood side by side in front of the house facing the prison. One of these was taken away, leaving only two.“We shall have Pierre over here this evening,” Gaston chuckled. “That’s the signal that I want him.”Sure enough, soon after dark, Pierre appeared. A few words explained the situation. He was off duty now for the night and free to do as he pleased.“Leave it to me,” he said. “I will be back in an hour.”He returned with a rough plan of the section of the prison in which Yvette was confined. Her cell occupied a corner on the first floor at the head of a flight of steps leading down to the big courtyard. If Yvette could get out of her cell it would be an easy matter to reach the door leading to the yard. But to get over the high wall, quite unclimbable, was a difficult problem. The entrance from the roadway was always guarded by two warders who occupied little separate lodges placed one each side the gateway.“I can get her out of her cell,” said Pierre, “but how to get her out of the yard I don’t know. I can get a false key to her during the day, but if I were found in that quarter of the prison at night it would mean instant dismissal. On that point the rules are inflexible and we cannot risk it.”“No,” said Gaston, “it is absolutely essential that you shall remain in the prison. But I think I can see a way.”He crossed the room to an old-fashioned bureau and produced from a drawer what looked like a heavy short-barrelled pistol.“Gas!” he said laconically, “fire that at a man’s face within five yards and he will drop like a log. It holds four shots and makes no noise. If Mademoiselle can get this she can knock out the two men at the lodge and easily slip out. You can bring her straight here, and we can hide her until she can get away.”“She cannot hide that in her cell,” said Pierre, “but I can hide it in the courtyard. Write her a letter telling her exactly what to do and where the pistol will be. I can slip into her cell a skeleton key which will open the door and also the door at the bottom of the steps. But you must manage the rest; I cannot do any more. She must get out immediately after the last visit of the warders at nine o’clock.”“Thanks very much, Pierre,” said Jules. “I can see no other way, and at all costs we must try to get her out. Neither my sister nor myself will ever forget.”Speedily a letter was written which gave Yvette full details of what was proposed, and Pierre was about to leave when Jules asked him if he had heard anything of the secret aeroplane.Pierre shook his head.“There are a lot of privately owned aeroplanes about here,” he said, “but I don’t know anything more than that. I have seen the one you refer to going up at night—the house is in plain view from my room on the first floor of the prison—but I never heard there was any secret about it, and there are so many aeroplanes about that no one takes any notice of them.”Jules told him all they had found out, and of their suspicions, and found Pierre was able to give them valuable information.The aeroplane shed, he told them, was just where Yvette had located it. Above it—and this was important—were some rooms which were used, apparently, as offices.“I have often,” said Pierre, “seen a man come from the offices with what looked like plans, make examination and measurements of the machine, and then go back. But I never took much notice; I had no reason to.”Pierre left, taking with him the letter to Yvette. For an hour Jules and Gaston discussed the situation.“We must get her out to-morrow,” declared Gaston, “or else they may take her away and we shall not be able to find out where she is. Manton ought to fly over to-morrow night. If we can get Mademoiselle Pasquet out she can hide here quite safely for a few hours, but there will be a very close search when her escape is discovered.”“I’ll get the message to Manton at once,” said Jules.And so it happened that Dick and Le Couteur, who had been waiting for hours in a state of tense anxiety, received a few minutes later the call.“M M M begins To-morrow night stop Come early as possible stop Three lights in triangle safe stop Four keep off M M M ends.”“At last,” said Dick grimly, with a look on his face that boded ill for some one. He looked drawn and haggard, and even Le Couteur could hardly repress a shudder at the savage determination that blazed in his eyes.For Yvette the next day was one of misery. Time after time she was dragged from her cell and taken before the Governor of the prison, and Kranzler, to be pitilessly cross-questioned and even threatened with violence. But even though she knew well that the two brutes were quite capable of carrying out their threats nothing could break the spirit of the French girl. To all their questions and menaces she turned a deaf ear and nothing they could say would induce her to affirm or deny anything. Utterly worn out she was at length roughly bundled back into her cell, where she dropped exhausted on the miserable apology for a bed. At least she was alone.It was about five o’clock and she had fallen into an uneasy doze, when she was awakened by a slight noise at the door. She saw the observation grille slide back and, pushed through the grating, a tiny parcel fell with a subdued clink on the floor. Then the grating was closed.Hastily she sprang to her feet and seized the parcel, a new hope surging in her breast. It could only mean help!Inside the parcel was a letter, unsigned of course, but in Jules’ handwriting, and a small key.Nine o’clock came, and with all the wearisome ceremony dear to the German heart, the guard, accompanied by a wardress, made its final inspection for the night. A few minutes after the big prison was as silent as the grave.Half an hour later Yvette cautiously fitted the key into the lock. It had been well oiled, and the door swung open without a sound. Creeping down the flight of steps Yvette found that the key also opened the door at the bottom, and in a moment she was in the yard.Rain was falling heavily. There was not a ray of light in the yard excepting a faint gleam which showed the position of the warders’ lodges.Before leaving her cell Yvette had pulled her stockings over her boots, and moving without a sound she groped her way along the wall. A few feet from the door she found the big stackpipe which brought the rain water from the roof. Stooping she lifted the iron grid of the drain and thrust in her hand. Her fingers closed on the butt end of the gas pistol.Silently, following along the wall in preference to crossing the courtyard, she stole towards the lodge. Complete surprise was essential.With the pistol ready in her hand, she softly opened the door of the lodge on the right of the gateway. Luck was with her again. The two men, in defiance of rules, were in the same lodge talking quietly.The noise of the door opening brought them to their feet with a jump. But they were too late. Only ten feet away from them Yvette pulled the trigger twice in rapid succession. There was no more noise than a slight hiss as the gas escaped and the two men dropped insensible. Snatching up a bunch of keys from the table, Yvette herself half-stifled, quickly got outside and closed the door. A moment later she had opened the wicket-gate and slipped through. She almost fell into the arms of Jules and Gaston, and at top speed the three raced through the rain for Gaston’s farm.Luckily, the pouring rain swiftly obliterated their footprints, but they had hardly got into hiding, wet through but triumphant, when pandemonium broke out in the prison, and the frantic ringing of the big bell announced the escape of a prisoner. The two warders, of course, had speedily recovered, and hastened to tell their story, and a quick search had revealed that Yvette’s cell was empty. A few minutes later search parties were hurrying in every direction in pursuit of the fugitive.Gaston’s farm, lying close to the prison, was naturally one of the first places to be visited. Gaston, smoking peacefully by the fireside, soon heard, as he expected, the savage clamour of dogs in the farmyard mingled with agonised cries for help.He hurried out. Two warders, one of them badly bitten, were backed against the fence, hardly keeping at bay with their sticks a couple of powerful dogs.Gaston called off the dogs and, full of apparent solicitude, expressed his regret. He listened to the guards’ explanation.“She cannot have been here,” he declared, “the dogs would have bitten her to pieces. But, of course, we will look round if you like.”The guards, however, were more than satisfied. Gaston’s argument was backed by their own experience, and they were quite ready to be convinced if they could only get away from the ferocious dogs who continually prowled about snarling as though even the presence of their master was hardly sufficient to protect his visitors. They little dreamed that the savage brutes would indeed have torn Yvette to pieces had not Gaston thoughtfully taken the precaution to lock them up before he and Jules started to rescue her!Away at Verdun Dick stood beside the Mohawk waiting impatiently in the dark. Time and again he had tested every nut and screw in the machine; time and again he had run the powerful engine to make sure that it was in working order.At last the longed for moment for action came. Anything was better than long drawn-out suspense.He wrung Le Couteur’s hand as he stepped into the machine.“I’ll be back with her by dawn,” he said, “or else—” there was no need to finish the sentence.He had not gone five minutes before Le Couteur received a message from Jules announcing that Yvette had escaped. If only Dick had known!It was raining hard when the Mohawk rose into the air, but Dick was beyond caring for the weather, and anxious only for Yvette, he sent the helicopter tearing through the darkness eastward to Berlin. He drove almost automatically, his thoughts intent on the girl ahead of him.As he approached Berlin, the weather cleared and the rain stopped. All around him were the navigation lights of the German mail and passenger planes, hurrying to every quarter of the Empire, and, even in his anxiety, Dick was conscious of an uneasy feeling of irritation at the thought that England was being left so far behind in the race for the mastery of the air.Then he caught sight of the great beams of light that marked the position of the huge Berlin aerodrome, and a few minutes’ flying brought him above Spandau. He circled twice, looking for Gaston’s signals, and at last he dropped lower, caught the gleam of the three lanterns which Gaston had placed to guide him, and brought the machine swiftly down beside the big barn. Then he leaped from his seat.He nearly gave a shout of joy that would have aroused every German within a mile! For there, in the light of the lanterns, stood Yvette herself.There was no time for explanation.“Now’s your chance,” gasped Jules, wild with excitement, “the German plane has just gone up!”Dick’s face hardened instantly.“Get in, Yvette,” he said curtly.Yvette stared in utter astonishment. This was a new Dick with a vengeance! All his usual graceful courtesy had dropped from him in the instant; the sheer fighting spirit was on top and Dick was, for the moment, the officer giving commands to his subordinates. His face was set like granite, and into the keen eyes there came a look Yvette had never seen there before. The cheerful, laughing “pal” had gone; in its place stood the fighting machine, pitiless and efficient.For an instant the girl was almost on the edge of rebellion; then she turned, and, without a word, took her place in the machine. As she did so, she caught Dick’s eye. For an instant the stern face relaxed; then the iron mask shut down again.For five minutes, while Yvette put on her leather helmet, Dick studied the plan which Jules showed to him by the light of a shaded lantern. When the Mohawk jumped into the air every detail of it was photographed indelibly on his brain.For three thousand feet the Mohawk shot upward at a speed which left Yvette dizzy and breathless. Then they hung motionless, as Dick peered anxiously earthward. Were they high enough?With a smothered exclamation Yvette pointed downward. Far below them a light was circling swiftly, darting hither and thither like a will o’ the wisp. No mail plane would behave like that. Dick decided that here was his quarry.Silently the Mohawk came down till it was not more than five hundred feet above its unsuspecting prey, the loud drone of whose engine came clearly on the air. Dick swung round in a circle, following every movement of the machine below, with a swift precision which Yvette keenly appreciated.Dick had made up his mind that the offices above the aeroplane shed probably held the key to the problem they had to solve. He knew he could destroy the machine itself. But that would not be enough if the plans remained intact; a new machine could quickly be built. If he could destroy the plans, on the other hand, there would be at least a lot of delay, which would enable the French agents to perfect their plans for discovering the secret. In all probability, he reasoned, the office would serve as the draughtsmen’s workroom, and if this were so, a well-placed bomb might destroy the labour of months.So he watched and waited, until at length they saw the German aeroplane going home. It came down in a wonderfully steep descent which was enough to tell Dick that the Germans had indeed made a discovery of great importance, and landed so slowly that Dick could hardly believe his eyes. But, at least, he saw enough to be sure that the descent was not the vertical drop of his own helicopter. His secret remained his own!Close beside the shed a couple of hooded airmen alighted. Lights were switched on and they began a careful examination of the machine. Five hundred feet above Dick watched the figures with interest.Suddenly the men below stiffened and looked skyward, listening intently. Evidently they had caught the faint sound of Dick’s propellers.A glance through his bomb sights showed Dick that he was in the position he desired. There was now no possible escape for the craft below.Then one of the men pointed upward. Even in the darkness he had caught a glimpse of the Mohawk.Dick’s hand shot to the bomb controls and he pulled a trigger. A petrol bomb fell squarely on the German plane and burst with a soft explosion, barely audible.A sheet of fire followed, and in an instant the German plane was a mass of flames, fed by the petrol which streamed from its tanks. One of the Germans was caught in the outburst and apparently died almost instantly.The second man, however, dashed into the office. The Mohawk moved forward a few feet and three more bombs fell in quick succession, right on the roof of the shed. Then, her work done, she rose high into the air and Dick and Yvette watched the results.The shed below them was already a furnace. Apparently there must have been some petrol tanks there, for no ordinary building could have burned so furiously. In a few minutes nothing remained but a heap of glowing embers.Dick watched keenly for the man who had run into the office, but he never reappeared, and it was evident that, trapped by the flames, he had been unable to get out in time, and had perished. Dick little suspected at the time how important the fate of that man was to prove.Then Dick set the Mohawk at top speed for home. Just as dawn was breaking Verdun loomed ahead. Yvette was saved.Two days later theBerliner Tageblatttold how the famous scientist, Professor Zingler, had perished in a fire which had destroyed his laboratory at Spandau. The fire was attributed to an explosion of petrol on the professor’s aeroplane which had set light to the office. Unfortunately, the paper added, all the professor’s valuable papers and books had been lost.The secret of the Zingler aeroplane had perished, and the seven dots were never heard again.

In a cosy little house at Veneux Nadon, near Moret-sur-Loing, in the great Forest of Fontainebleau, Dick, Yvette, and Jules were seated in earnest conversation. They made a remarkable trio. Dick was unmistakably English, Yvette and her brother as unmistakably French—the girl dark-haired and dark-eyed, and with all the grace and vivacity which distinguish Frenchwomen of the better class. Her brother, quiet and dreamy, lacked his sister’s vivacity, but there was a suggestion of strength and iron resolution in the firm mouth and steely eyes.

“It will be terribly dangerous, Dick,” said Yvette, with an altogether new note of anxiety in her voice.

“I suppose it will,” replied Dick, “but,”—and his voice hardened as he spoke—“I don’t see what else we can do. We cannot run the risk of seeing a perfected helicopter in German hands. It would be too fearful a weapon. We must get hold of the plans and destroy the machine, whatever the risk may be.”

Strange stories had come through the French Secret Service of a new and wonderful type of aircraft which was being tested with the utmost secrecy somewhere in the neighbourhood of Spandau, the great military town near Berlin. Of its precise character little was known or could be ascertained, and even Regnier, the astute and energetic head of the French Secret Service, had at length to confess himself utterly beaten. His cleverest agents had been baffled; more than one was in a German prison, with little hope of an early release. In the meantime the mysterious machine flitted about the neighbourhood of the great garrison, always at night, appearing and disappearing under circumstances which proved conclusively that it must be of a type which differed widely from any yet known to the public.

“We must go, Dick,” said Yvette, “and Regnier is extremely anxious that you should help us. His trouble is that while he has dozens of capable men at his command none of them has a really expert knowledge of aviation. He thinks that if you once got a good look at the machine you could form a complete idea of what it really is.”

“Very well,” said Dick, “we will look upon it as settled. We must work out a plan.”

For many months Dick Manton had been working steadily and secretly at Veneux Nadon under the auspices, though not actually in the employ, of the French Secret Service. He had offered the plans of the Mohawk to the British War Office, only to be met with a reception so chilly as effectually to discourage him from proceeding further in the matter. Regnier, however, was a man of a different stamp from the British bureaucrat—keen as mustard and with the saving touch of imagination which is characteristic of the best type of Frenchman. He had unbounded faith in Yvette, who had for some time been one of his most trusted lieutenants, and when, angry at the attitude of the British War Office, she had given him a hint of what the Mohawk could really do, he had offered Dick the fullest facilities for continuing his work. Under the circumstances Dick had felt that to refuse would have been absurd.

Veneux Nadon was a lonely little spot. Here Dick, though only thirty miles from Paris, found himself in complete seclusion, with a well-equipped workshop in large grounds completely buried in the lovely forest, and thoroughly screened from prying eyes. Regnier had put the matter to him quite plainly.

“You are an Englishman, Monsieur Manton,” he had said, “and I will not ask you to sell your secret to France. But we are willing to bear the expense of perfecting your invention on the distinct understanding that when the time comes England shall have the option of sharing in it to the exclusion of all other countries except France. When you are ready we will officially invite the British Government to send a representative and will give them the opinion of coming in on equal terms. I do not think we can do more or less.”

So it was settled, and for many months Dick and Jules had toiled on the building of a new Mohawk whose performances far surpassed those of the machine lost in the Adriatic. It was now completed and its preliminary tests had satisfied them that they had forged a weapon of tremendous potency.

The machine was of the helicopter type. The idea, of course, was not new, but Dick had solved a problem which for many years had baffled inventors whose dream it was to construct a machine which should have the power of rising vertically from the ground and remaining stationary in the air.

Driven upward by powerful propellers placed horizontally underneath the body, the Mohawk was capable of rising from the ground at a tremendous speed. Once in the air the lifting propellers were shut off and the machine moved forward under the impulse of the driving screws placed in the front and rear. These screws were the secret of Dick Manton’s triumph. They were of a new design, giving a tremendous ratio of efficiency. In size they wore relatively tiny, but possessed far greater power than any propeller known. The machine itself was nearly square. The body was completely covered by the big, single plane, measuring about twenty feet each way. This was the outside size of the machine and so perfectly was the helicopter controlled that Dick had repeatedly brought it to earth in a marked space not more than thirty-two feet square.

Fitted with the new silencer which Dick had discovered and applied to the old Mohawk with such signal success, the engine was practically noiseless. At high speed the tiny propellers emitted only a thin, wailing note, barely audible a few yards away. Time and again Dick had sailed on dark nights only a few feet above the house roofs of Paris and had found that the noise of the ordinary traffic was amply sufficient to prevent his presence being discovered.

To ensure absolute secrecy the various parts of the machine had been made in widely separated districts of France, and had been brought from Paris to Veneux Nadon, where Dick and Jules had carried out the erection of the machine alone. The very existence of the new aeroplane was utterly unsuspected by the few villagers who lived in the neighbourhood.

Keenly interested in his work Dick had thoroughly enjoyed the peaceful life in the depths of the beautiful forest. He and Jules had become the closest of friends, and with Yvette, whose winning personality seemed to bind him to her more closely day by day, they made up a happy house party. They were looked after by a capable old peasant woman who was the devoted slave of all three, but whose admiration for Yvette seemed to rise almost to the point of veneration.

On the day following the conversation recorded above, they were surprised to receive a visit from Regnier himself—an alert, dark-eyed man who seemed seriously perturbed.

“There is no time to be lost,” he declared. “I hear to-day from Gaston that he has managed to get a near view of the new German machine. He says it rose apparently from the flat roof of a house standing in its own grounds outside Spandau. He happened to be near and caught sight of it just in time. Of course it was dark and he could see no details. But he is positive that the machine rose nearly straight up from the flat roof at an angle far too steep for any of our machines. That alone is sufficient to show that the Germans have got hold of something new and valuable. He waited for a long time, and finally saw the machine return. He declares it landed again on the roof. Evidently, Monsieur Manton, they have found out something along the lines of your invention, even if they have not actually got your secret.”

“How far away was Gaston when he saw it?” asked Dick.

“It must have been at least a quarter of a mile,” replied Regnier, “as the grounds are very extensive. Gaston dared not venture an attempt to get inside; the high fence is utterly unscalable, and the two lodge gates are always kept locked and there is a keeper at each.”

“And he heard the engine?”

“Yes, he says so specifically,” replied the Chief.

“Well,” said Dick, “at any rate we are ahead of them to that extent. If it had been my machine he would not have heard the engine at all at that distance.”

“However,” he went on, “it is evidently time we acted. Now, Monsieur Regnier, Mademoiselle Pasquet has told me what you want. I am willing to go. But I shall have to take the Mohawk. How are we to hide it? I can get over and back at night safely enough, but to hide the machine in the day-time will be another matter.”

“Gaston can arrange that,” the Chief declared. “You know he has a farm a short distance outside, Spandau. There is a big barn there with no sides, and your machine can be easily dragged into it and concealed during the day. You know Gaston is passing as a German farmer. He has acted for years for us in this way and has never even been suspected. But you could not stay long.”

“Very good,” said Dick. “I think the best plan will be for Jules to go by motor and for Mademoiselle to go separately by train. They must find out somehow exactly where the German plane is lodged and, if possible, where the plans are likely to be kept, and I must act accordingly. In any case, there will be no difficulty in smashing up the machine, but unless we destroy the plans as well they will be building another too soon to suit us. I will go to Verdun and wait there with the Mohawk until the time comes for me to fly over.”

Jules and Yvette left the next day. Jules’ car was quite an ordinary one, but it had one important detail added. In the hollow flooring was cunningly concealed a small but powerful wireless telegraph set, the power for which was supplied by the engine. It was highly efficient, but had one serious drawback; it could only be used while the car was at rest owing to the necessity for running an aerial wire up some tall structure, such as a building or a tree. This, in a country where every one was specially suspicious of spies, was a serious peril.

Three days later seven mysterious dots began to excite the ungovernable curiosity of the wireless world!

Jules and Yvette, on arrival in Berlin, had taken rooms adjoining one another at the “Adlon,” the big cosmopolitan hotel which is always crowded with visitors from every country under the sun. Yvette posed as a school teacher on an educational tour, but her position was one of great danger. It was impossible to disguise her face, and although she had done what she could to destroy her French individuality by wearing peculiarly hideous German clothes, there was the ever-present danger that she would be seen and recognised by some of the many German agents who during the war had learnt to know her features, and who had good reason to remember her daring exploits in Alsace.

At the same time, in order to have a possible retreat in a humbler neighbourhood, Yvette had hired a room in one of the mean quarters of the town, putting in a few miserable sticks of furniture and giving out that she was a sempstress employed at one of the big shops.

She and Jules had decided never to speak in public. It was essential, however, that they should be able to communicate freely, and through the wall between their rooms Jules had bored with a tiny drill a hole through which he had passed a wire of a small pocket telephone. They could thus talk with ease and with the doors of their rooms locked they were absolutely safe from detection so long as they spoke in a whisper.

It was on a dark night, the sky obscured by heavy masses of clouds, that Dick rose in the Mohawk from the Forest of Fontainebleau and headed for Verdun. A couple of hours’ flying brought him over the fortress and he descended in a clearing in a dense wood where he was welcomed by Captain Le Couteur, the chief engineer of the military wireless station. Covered with big tarpaulins, the Mohawk was left under the guard of a dozen Zouaves, and Dick and Captain Le Couteur motored to the citadel.

Here the Captain took Dick directly into the steel-walled chamber deep under the fortifications which was the brain of the defences of Verdun. It was the nucleus of the entire system of telegraph and telephone wires which, in time of war, would keep the commander of the troops in the district fully informed of everything that was happening in every sector of the defences. The innermost room of all, where none but the Captain himself had access, contained the secret codes which dozens of foreign agents would have willingly risked their lives to possess. Their efforts—and they knew it—would have been in vain, for the chamber was guarded day and night by a band of picked men whose fidelity to France was utterly beyond the possibility of suspicion.

“Your messages have already started—the seven dots at intervals of seven seconds,” said Captain Le Couteur when they were comfortably seated in the innermost room. “I got half a dozen test calls last night and everything seems to be working well. I expect they are arousing some interest, for operators all over Europe will be mystified. There will be another call about nine o’clock and in the meantime you had better get some sleep. I will call you if anything happens.”

Dick stretched himself on a couch and slept peacefully. Nine o’clock found him with Captain Le Couteur seated in the innermost room at a table covered with delicate wireless apparatus. Turning a switch, the Captain lit up the row of little valves, put the receiving set in operation, and assuming one headpiece himself, handed another to Dick.

He placed his hand upon one of the ebonite knobs of the complicated apparatus and slowly turned it. Then he turned a second condenser very carefully.

“We are on the ordinary six-hundred-metre wave-length now,” the Captain explained, “and shall remain so until we get our seven dots. I am bound to keep the machine so or I should miss other messages I ought to hear. But we will change as soon as we get your signal.”

Presently they came, sharp and clear, dot-dot-dot-dot-dot-dot-dot. Immediately Captain Le Couteur made some swift adjustments.

“Now listen,” he said, “we are on a three-hundred-and-fifty-metre wave-length.”

A moment later came three M’s—three pairs of dashes.

“That’s Code Five,” said Captain Le Couteur. “Now we shall get the real message.”

It came in what to Dick was a gibberish of letters and figures, but Captain le Couteur wrote it down and then, decoding it, read it off with the skill of the expert. It ran:

“M M M begins Have located the machine stop Apparently entirely new type stop Tell Manton to be ready stop M M M ends.”

“M M M begins Have located the machine stop Apparently entirely new type stop Tell Manton to be ready stop M M M ends.”

“That’s our newest code,” the Captain explained, “and this is the first time it has been used. Jules learnt it only just before he left. It is very unlikely that the message has been picked up by anyone else, as the wave-length is quite low, but even if it was, no one could decipher the code from such a short message. They would want one very much longer, and even then it would probably take at least a week or ten days of very hard work by a lot of experts.”

And he paused.

“I think it would be well now for one of us to be constantly here,” he went on. “Perhaps, too, you would like to overhaul your machine so as to have it absolutely ready to get away at a moment’s notice. My fellows will give you any help you want and they are all absolutely to be depended upon not to talk.”

Dick soon had the Mohawk ready; indeed there was not much to do after such a short trip as the flight to Verdun. The rest of the day he spent chatting with Captain Le Couteur, finding him a delightful companion and full of enthusiasm on the subject of wireless, of which his knowledge seemed boundless. Dick felt he could never tire of admiring the wonderfully ingenious devices which the other had invented and put into operation in his underground fortress.

Several more messages, chiefly brief reports, were received from Jules, always heralded by the seven dots and begun with the three M’s which signified the secret code number Five. For a few hours everything seemed to be going well. Then, towards evening came graver news, which on being deciphered, read:

“M M M begins Much fear Yvette suspected stop Tell Manton to be ready instant action stop M M M ends.”

“M M M begins Much fear Yvette suspected stop Tell Manton to be ready instant action stop M M M ends.”

It could only mean, they realised, that Yvette had been recognised by a German agent and was being closely watched. The position was dangerous.

Dick spent the next few hours in an agony of suspense. But he could do nothing. His first instinct was to fly to Berlin. But Le Couteur’s iron common-sense showed him clearly enough that to do so would be futile. To keep the Mohawk in Germany, even for a single day, would be risky; to try to hide her there for perhaps a week till they got a chance to rescue Yvette would be suicidal.

A sudden swoop, swift and relentless action, and a quick escape were the essentials of success.

Captain Le Couteur was scarcely less anxious than Dick himself. He had known Yvette since she was a child; they came from the same town in Alsace. But he possessed a brain of ice and restrained Dick’s impetuosity, though guessing shrewdly at its cause.

“The time is not come yet,” he declared. “This is a bit of business which must go to the last tick of the dock. Mademoiselle herself would never forgive us if we spoilt everything by undue precipitation, and, after all, Monsieur Manton, France is of even more importance than Mademoiselle Pasquet, much as I admire her.”

“I know,” Dick admitted. “But when I think of her, with her war record, which they know all about, falling into the hands of those brutes, I can hardly sit still.”

“They have not got her yet and she is very clever,” replied Le Couteur. “Let us hope that she will give them the slip.”

But about ten o’clock the following morning the dreaded blow fell.

They were seated in the underground chamber, Dick ill at ease and full of gloomy forebodings. The apparatus set to receive messages on three-hundred-and-fifty-metres. Suddenly a buzzing noise was emitted from the loud-speaking telephone on the bench.

Seven dots, seven times repeated, clicked out strong and dear!

Surely seconds had never passed so slowly! It seemed an age before Captain Le Couteur, his face white as chalk, took down the message which followed, and then referring to the code, read:

“Yvette arrested this morning by Kranzler.”

Dick turned dizzy and the room spun round him as the dreadful significance of the words struck him. Kranzler, of all men! The murderer of Yvette’s father and mother, the man whom she had beaten over and over again at his own game of espionage during the war, the man whose sensational attempt to dispose of Rasputin’s stolen jewels had been foiled by Yvette’s skill and daring! He was, as they knew, a desperate brute who would stick at nothing to feed his revenge.

Dick was rushing from the room, determined at all hazards to leave for Berlin at once, when Le Couteur seized his arm in a grip of iron.

“Steady, Manton,” he said sharply. “Don’t be a fool. You’ll spoil everything. Sit down and wait for more news.”

The words brought Dick to his senses.

“I’m sorry, Le Couteur,” he said, “but I think I went a bit mad. You are quite right. But Kranzler—of all men! You know the story, of course?”

Le Couteur nodded.

“It could hardly be worse,” he admitted, “and there’s no use disguising the fact. But we must wait for more from Jules. In the meantime I am going to talk to Regnier. He must have more men on the spot. At all costs Mademoiselle must be rescued.”

They were soon in touch with the Chief in Paris, who was horrified at the news.

“I will get some more men over at once,” he said. “But we can do nothing until we find out where they have taken her. Jules will realise that. You are certain to get another message from him before long.”

It was not until later that day that they learned how the arrest had been effected. Yvette, as soon as the position of the German plane had been located, had managed in the guise of a girl seeking work, to scrape acquaintance with one of the maids employed at the big house where the aeroplane was lodged. The girl had actually taken her up to the house and Yvette had coolly applied to the housekeeper for employment. There was, as it happened, no vacancy, but Yvette had used her eyes to good purpose. In the walk from the lodge to the house and back she had caught sight of the shed in which, obviously, the aeroplane was housed, and had noted its exact position in the extensive grounds. Hurrying back to the hotel she had communicated this information to Jules and both were filled with excitement at the important step forward they had made.

Sitting in the lounge of the “Adlon” next morning Jules had seen Kranzler enter. He had started at once to warn Yvette to “lie low,” but was just too late. Yvette at that moment came down the staircase and before Jules could interpose had met Kranzler face to face. She was instantly recognised.

With a grin of delight on his evil face the big German bowed profoundly.

“This is indeed a pleasure, Mademoiselle Pasquet!” he said ironically.

Yvette very coolly tried to carry it off.

“Monsieur has, I think, made a mistake,” she said in German.

“It’s no use, Mademoiselle,” was the harsh reply, “I know you perfectly. You must come with me—or shall I call the police?”

There was obviously nothing for it but to obey, and Yvette was forced to leave the hotel in the clutches of the one man in all Germany she had the greatest reason to fear.

Jules acted promptly. Slipping out of the hotel he hurriedly wheeled to the front a motor-bicycle he had hired to enable him to travel speedily between Berlin and Spandau. He got round just in time to see Kranzler put Yvette into a taxi, and followed them until they alighted at the door of the house in the Koeniggratzer-strasse which was the head-quarters of the German Secret Service. Yvette was taken inside.

To get the news to Dick was now Jules’ first consideration. Knowing something of the methods of the German Secret Service he was reasonably sure that Yvette would be put through a long examination before she was taken to prison, and he decided to run the risk of being absent for a short time to get his message away. He drove hastily in his car out into the country until he found a tree to which his aerial wire could be attached and got off the brief message which conveyed the news to Verdun. Then he returned to watch, and ascertain where Yvette was to be imprisoned.

The taxi was still outside the door when he got back to the Koeniggratzer-strasse. As an excuse for waiting he feigned engine trouble and tinkered with his machine, keeping all the time a close watch on the door opposite.

He had not long to wait. In about half an hour Yvette was brought out, still in the custody of Kranzler, and driven away. Jules followed, and, at length, had the satisfaction of knowing that Yvette was in the big prison outside Spandau. It was a melancholy satisfaction, it is true, but to know where she was was of supreme importance.

Driving to Gaston’s farm he soon informed Verdun where Yvette was located and then turned to discuss the position with Gaston.

To his intense surprise and delight, Gaston was able to give him some comfort.

“Of course, it is a great misfortune,” he said, “but it might be worse. They have taken her to the one prison in Germany where we have been able to keep a thoroughly trustworthy agent. He is a warder who passes as Herman Fuchs; his real name is Pierre Latour. We shall soon know all about Mademoiselle.”

The front of the prison was in dear view from Gaston’s farm. Going outside, he called on Jules to help him to move one of three large barrels, each containing a big flowering shrub, which stood side by side in front of the house facing the prison. One of these was taken away, leaving only two.

“We shall have Pierre over here this evening,” Gaston chuckled. “That’s the signal that I want him.”

Sure enough, soon after dark, Pierre appeared. A few words explained the situation. He was off duty now for the night and free to do as he pleased.

“Leave it to me,” he said. “I will be back in an hour.”

He returned with a rough plan of the section of the prison in which Yvette was confined. Her cell occupied a corner on the first floor at the head of a flight of steps leading down to the big courtyard. If Yvette could get out of her cell it would be an easy matter to reach the door leading to the yard. But to get over the high wall, quite unclimbable, was a difficult problem. The entrance from the roadway was always guarded by two warders who occupied little separate lodges placed one each side the gateway.

“I can get her out of her cell,” said Pierre, “but how to get her out of the yard I don’t know. I can get a false key to her during the day, but if I were found in that quarter of the prison at night it would mean instant dismissal. On that point the rules are inflexible and we cannot risk it.”

“No,” said Gaston, “it is absolutely essential that you shall remain in the prison. But I think I can see a way.”

He crossed the room to an old-fashioned bureau and produced from a drawer what looked like a heavy short-barrelled pistol.

“Gas!” he said laconically, “fire that at a man’s face within five yards and he will drop like a log. It holds four shots and makes no noise. If Mademoiselle can get this she can knock out the two men at the lodge and easily slip out. You can bring her straight here, and we can hide her until she can get away.”

“She cannot hide that in her cell,” said Pierre, “but I can hide it in the courtyard. Write her a letter telling her exactly what to do and where the pistol will be. I can slip into her cell a skeleton key which will open the door and also the door at the bottom of the steps. But you must manage the rest; I cannot do any more. She must get out immediately after the last visit of the warders at nine o’clock.”

“Thanks very much, Pierre,” said Jules. “I can see no other way, and at all costs we must try to get her out. Neither my sister nor myself will ever forget.”

Speedily a letter was written which gave Yvette full details of what was proposed, and Pierre was about to leave when Jules asked him if he had heard anything of the secret aeroplane.

Pierre shook his head.

“There are a lot of privately owned aeroplanes about here,” he said, “but I don’t know anything more than that. I have seen the one you refer to going up at night—the house is in plain view from my room on the first floor of the prison—but I never heard there was any secret about it, and there are so many aeroplanes about that no one takes any notice of them.”

Jules told him all they had found out, and of their suspicions, and found Pierre was able to give them valuable information.

The aeroplane shed, he told them, was just where Yvette had located it. Above it—and this was important—were some rooms which were used, apparently, as offices.

“I have often,” said Pierre, “seen a man come from the offices with what looked like plans, make examination and measurements of the machine, and then go back. But I never took much notice; I had no reason to.”

Pierre left, taking with him the letter to Yvette. For an hour Jules and Gaston discussed the situation.

“We must get her out to-morrow,” declared Gaston, “or else they may take her away and we shall not be able to find out where she is. Manton ought to fly over to-morrow night. If we can get Mademoiselle Pasquet out she can hide here quite safely for a few hours, but there will be a very close search when her escape is discovered.”

“I’ll get the message to Manton at once,” said Jules.

And so it happened that Dick and Le Couteur, who had been waiting for hours in a state of tense anxiety, received a few minutes later the call.

“M M M begins To-morrow night stop Come early as possible stop Three lights in triangle safe stop Four keep off M M M ends.”

“M M M begins To-morrow night stop Come early as possible stop Three lights in triangle safe stop Four keep off M M M ends.”

“At last,” said Dick grimly, with a look on his face that boded ill for some one. He looked drawn and haggard, and even Le Couteur could hardly repress a shudder at the savage determination that blazed in his eyes.

For Yvette the next day was one of misery. Time after time she was dragged from her cell and taken before the Governor of the prison, and Kranzler, to be pitilessly cross-questioned and even threatened with violence. But even though she knew well that the two brutes were quite capable of carrying out their threats nothing could break the spirit of the French girl. To all their questions and menaces she turned a deaf ear and nothing they could say would induce her to affirm or deny anything. Utterly worn out she was at length roughly bundled back into her cell, where she dropped exhausted on the miserable apology for a bed. At least she was alone.

It was about five o’clock and she had fallen into an uneasy doze, when she was awakened by a slight noise at the door. She saw the observation grille slide back and, pushed through the grating, a tiny parcel fell with a subdued clink on the floor. Then the grating was closed.

Hastily she sprang to her feet and seized the parcel, a new hope surging in her breast. It could only mean help!

Inside the parcel was a letter, unsigned of course, but in Jules’ handwriting, and a small key.

Nine o’clock came, and with all the wearisome ceremony dear to the German heart, the guard, accompanied by a wardress, made its final inspection for the night. A few minutes after the big prison was as silent as the grave.

Half an hour later Yvette cautiously fitted the key into the lock. It had been well oiled, and the door swung open without a sound. Creeping down the flight of steps Yvette found that the key also opened the door at the bottom, and in a moment she was in the yard.

Rain was falling heavily. There was not a ray of light in the yard excepting a faint gleam which showed the position of the warders’ lodges.

Before leaving her cell Yvette had pulled her stockings over her boots, and moving without a sound she groped her way along the wall. A few feet from the door she found the big stackpipe which brought the rain water from the roof. Stooping she lifted the iron grid of the drain and thrust in her hand. Her fingers closed on the butt end of the gas pistol.

Silently, following along the wall in preference to crossing the courtyard, she stole towards the lodge. Complete surprise was essential.

With the pistol ready in her hand, she softly opened the door of the lodge on the right of the gateway. Luck was with her again. The two men, in defiance of rules, were in the same lodge talking quietly.

The noise of the door opening brought them to their feet with a jump. But they were too late. Only ten feet away from them Yvette pulled the trigger twice in rapid succession. There was no more noise than a slight hiss as the gas escaped and the two men dropped insensible. Snatching up a bunch of keys from the table, Yvette herself half-stifled, quickly got outside and closed the door. A moment later she had opened the wicket-gate and slipped through. She almost fell into the arms of Jules and Gaston, and at top speed the three raced through the rain for Gaston’s farm.

Luckily, the pouring rain swiftly obliterated their footprints, but they had hardly got into hiding, wet through but triumphant, when pandemonium broke out in the prison, and the frantic ringing of the big bell announced the escape of a prisoner. The two warders, of course, had speedily recovered, and hastened to tell their story, and a quick search had revealed that Yvette’s cell was empty. A few minutes later search parties were hurrying in every direction in pursuit of the fugitive.

Gaston’s farm, lying close to the prison, was naturally one of the first places to be visited. Gaston, smoking peacefully by the fireside, soon heard, as he expected, the savage clamour of dogs in the farmyard mingled with agonised cries for help.

He hurried out. Two warders, one of them badly bitten, were backed against the fence, hardly keeping at bay with their sticks a couple of powerful dogs.

Gaston called off the dogs and, full of apparent solicitude, expressed his regret. He listened to the guards’ explanation.

“She cannot have been here,” he declared, “the dogs would have bitten her to pieces. But, of course, we will look round if you like.”

The guards, however, were more than satisfied. Gaston’s argument was backed by their own experience, and they were quite ready to be convinced if they could only get away from the ferocious dogs who continually prowled about snarling as though even the presence of their master was hardly sufficient to protect his visitors. They little dreamed that the savage brutes would indeed have torn Yvette to pieces had not Gaston thoughtfully taken the precaution to lock them up before he and Jules started to rescue her!

Away at Verdun Dick stood beside the Mohawk waiting impatiently in the dark. Time and again he had tested every nut and screw in the machine; time and again he had run the powerful engine to make sure that it was in working order.

At last the longed for moment for action came. Anything was better than long drawn-out suspense.

He wrung Le Couteur’s hand as he stepped into the machine.

“I’ll be back with her by dawn,” he said, “or else—” there was no need to finish the sentence.

He had not gone five minutes before Le Couteur received a message from Jules announcing that Yvette had escaped. If only Dick had known!

It was raining hard when the Mohawk rose into the air, but Dick was beyond caring for the weather, and anxious only for Yvette, he sent the helicopter tearing through the darkness eastward to Berlin. He drove almost automatically, his thoughts intent on the girl ahead of him.

As he approached Berlin, the weather cleared and the rain stopped. All around him were the navigation lights of the German mail and passenger planes, hurrying to every quarter of the Empire, and, even in his anxiety, Dick was conscious of an uneasy feeling of irritation at the thought that England was being left so far behind in the race for the mastery of the air.

Then he caught sight of the great beams of light that marked the position of the huge Berlin aerodrome, and a few minutes’ flying brought him above Spandau. He circled twice, looking for Gaston’s signals, and at last he dropped lower, caught the gleam of the three lanterns which Gaston had placed to guide him, and brought the machine swiftly down beside the big barn. Then he leaped from his seat.

He nearly gave a shout of joy that would have aroused every German within a mile! For there, in the light of the lanterns, stood Yvette herself.

There was no time for explanation.

“Now’s your chance,” gasped Jules, wild with excitement, “the German plane has just gone up!”

Dick’s face hardened instantly.

“Get in, Yvette,” he said curtly.

Yvette stared in utter astonishment. This was a new Dick with a vengeance! All his usual graceful courtesy had dropped from him in the instant; the sheer fighting spirit was on top and Dick was, for the moment, the officer giving commands to his subordinates. His face was set like granite, and into the keen eyes there came a look Yvette had never seen there before. The cheerful, laughing “pal” had gone; in its place stood the fighting machine, pitiless and efficient.

For an instant the girl was almost on the edge of rebellion; then she turned, and, without a word, took her place in the machine. As she did so, she caught Dick’s eye. For an instant the stern face relaxed; then the iron mask shut down again.

For five minutes, while Yvette put on her leather helmet, Dick studied the plan which Jules showed to him by the light of a shaded lantern. When the Mohawk jumped into the air every detail of it was photographed indelibly on his brain.

For three thousand feet the Mohawk shot upward at a speed which left Yvette dizzy and breathless. Then they hung motionless, as Dick peered anxiously earthward. Were they high enough?

With a smothered exclamation Yvette pointed downward. Far below them a light was circling swiftly, darting hither and thither like a will o’ the wisp. No mail plane would behave like that. Dick decided that here was his quarry.

Silently the Mohawk came down till it was not more than five hundred feet above its unsuspecting prey, the loud drone of whose engine came clearly on the air. Dick swung round in a circle, following every movement of the machine below, with a swift precision which Yvette keenly appreciated.

Dick had made up his mind that the offices above the aeroplane shed probably held the key to the problem they had to solve. He knew he could destroy the machine itself. But that would not be enough if the plans remained intact; a new machine could quickly be built. If he could destroy the plans, on the other hand, there would be at least a lot of delay, which would enable the French agents to perfect their plans for discovering the secret. In all probability, he reasoned, the office would serve as the draughtsmen’s workroom, and if this were so, a well-placed bomb might destroy the labour of months.

So he watched and waited, until at length they saw the German aeroplane going home. It came down in a wonderfully steep descent which was enough to tell Dick that the Germans had indeed made a discovery of great importance, and landed so slowly that Dick could hardly believe his eyes. But, at least, he saw enough to be sure that the descent was not the vertical drop of his own helicopter. His secret remained his own!

Close beside the shed a couple of hooded airmen alighted. Lights were switched on and they began a careful examination of the machine. Five hundred feet above Dick watched the figures with interest.

Suddenly the men below stiffened and looked skyward, listening intently. Evidently they had caught the faint sound of Dick’s propellers.

A glance through his bomb sights showed Dick that he was in the position he desired. There was now no possible escape for the craft below.

Then one of the men pointed upward. Even in the darkness he had caught a glimpse of the Mohawk.

Dick’s hand shot to the bomb controls and he pulled a trigger. A petrol bomb fell squarely on the German plane and burst with a soft explosion, barely audible.

A sheet of fire followed, and in an instant the German plane was a mass of flames, fed by the petrol which streamed from its tanks. One of the Germans was caught in the outburst and apparently died almost instantly.

The second man, however, dashed into the office. The Mohawk moved forward a few feet and three more bombs fell in quick succession, right on the roof of the shed. Then, her work done, she rose high into the air and Dick and Yvette watched the results.

The shed below them was already a furnace. Apparently there must have been some petrol tanks there, for no ordinary building could have burned so furiously. In a few minutes nothing remained but a heap of glowing embers.

Dick watched keenly for the man who had run into the office, but he never reappeared, and it was evident that, trapped by the flames, he had been unable to get out in time, and had perished. Dick little suspected at the time how important the fate of that man was to prove.

Then Dick set the Mohawk at top speed for home. Just as dawn was breaking Verdun loomed ahead. Yvette was saved.

Two days later theBerliner Tageblatttold how the famous scientist, Professor Zingler, had perished in a fire which had destroyed his laboratory at Spandau. The fire was attributed to an explosion of petrol on the professor’s aeroplane which had set light to the office. Unfortunately, the paper added, all the professor’s valuable papers and books had been lost.

The secret of the Zingler aeroplane had perished, and the seven dots were never heard again.

Chapter Four.The Sorcerer of Soho.“Unless we can solve this terrible mystery in the course of a few weeks, it is hardly too much to say that England is doomed.”The speaker was the white-haired Professor Durward, the distinguished head of the Royal Society. He sat facing the Prime Minister in the latter’s room at 10, Downing Street. Round the long table were grouped the members of the Cabinet. They were men who had lived through stormy and troublous times and had met stories of disaster without flinching. But, as they admitted afterwards, none of the terrible tidings of past years, when the fortunes of the Empire seemed to be tottering, had affected them to the same extent as the few brief words with which the distinguished savant summed up the long deliberations on which they had been engaged. They seemed pregnant with the very message of Fate. Almost they could see the writing on the wall.“But, Professor,” asked the Premier, “do you really mean that nothing whatever can be done to check or prevent this terrible malady?”“Nothing, so far as I am aware,” was the reply. “As you know the most distinguished men of science in England have been at work on the problem. We had a very full meeting last night, and the unanimous verdict was that the disease was not only absolutely incurable, but that nothing we have tried seems capable of affording even the slightest alleviation. The deaths reported already amount to nearly half a million; though the truth is being carefully concealed from the public in order to allay panic, yet practically every community in which the disease has appeared has been virtually wiped out. Curiously enough it does not seem to be spread by contagion. In spite of the rush of terrified people from districts in which it has appeared, no cases have shown themselves except in towns or villages where the mysterious violet cloud has been observed. That phenomenon has been the precursor of every outbreak.”A month before, in the tiny village of Moorcrest, buried in the recesses of the Chilterns, an unoccupied house had suddenly collapsed with a slight explosion. No one was in the house at the time, and no one was injured. As to the cause of the explosion no one could form an idea. Nothing in the nature of the remains of a bomb could be discovered, and there was no gas laid on in the village.But the few villagers who were about at the time spoke of seeing a dense cloud of pale violet vapour pouring from the ruins. On this point all observers were agreed, and they all agreed, too, that the cloud was accompanied by a powerful smell which strongly resembled a combination of petrol and musk. That was all the evidence that could be collected. No harm seemed to follow and the matter was speedily forgotten.Very soon, however, the incident took on a new and sinister significance.A week later a similar explosion took place in Ancoats, a poor and densely crowded suburb of Manchester. In every respect this incident duplicated the happening at Moorcrest. Naturally, it created something of a sensation, and the papers, recalling the Moorcrest mystery, made the most of it.During the next fortnight similar explosions, all bearing the same distinguishing features, occurred in various parts of England. Sometimes there would be three or four in a single day in the same, or closely adjoining, areas. The public became excited. Not a single person was injured, the damage done was apparently trifling, since all the houses destroyed were of the poorest class. It looked like the work of a maniac—purposeless and without the slightest trace of a motive. People spoke of Bolshevists and Communists. But what Bolshevik or Communist, others asked, would waste time and effort to inflict such absurd pinpricks on Society?They were soon to be undeceived. An enemy of Society was indeed at work armed with a weapon of a potency which far outstripped the paltry efforts of the Terrorists of old, to whom the bomb and the revolver were the means of world regeneration.The explosion at Moorcrest took place on May 2nd.Twelve days later, on May 14th, Doctor Clare-Royden, who was in practice at Little Molton, a village about four miles from Moorcrest, received an urgent message from an old patient summoning him to Moorcrest.Doctor Royden, jumping on his motor-bicycle, answered the summons at once. A terrible surprise awaited him.Practically every inhabitant of the village, about a hundred people in all, were in the grip of a fearful and, so far as Doctor Royden’s knowledge went, wholly unknown malady.Its principal symptoms were complete paralysis of the arms which were strained and twisted in a terrible manner, fever which mounted at a furious speed, and agonising pains in the head. Many of the victims were alreadyin extremis, several died even while the doctor was examining them, and in the course of a few hours practically everyone attacked by the disease had succumbed. The only ones to recover were a few children, too young to give any useful information.It would be useless to trace or describe the excitement which followed, even though the Press, at the instigation of the Government, was silent upon the matter. Help was rushed to Moorcrest, the dead were interred and the living helped in every way. The Ministry of Health sent down its most famous experts to investigate. One and all admitted that they were completely baffled.On May 21st Ancoats was the scene of an appalling outbreak of the disease. People in the densely packed areas died like flies. But there were some remarkable circumstances which drew the attention of the trained observers who rushed to the spot to inquire into the phenomenon.Ancoats had been the scene of the second explosion twelve days before. It was not long before a health official noticed the coincidence that the outbreaks at Moorcrest and Ancoats occurred exactly twelve days after the explosions in each place.The coincidence was, of course, remarked upon as somewhat suspicious, but it was not until it was reproduced in the terrible outbreak at Nottingham that suspicion became a practical certainty. It was speedily confirmed by repeated outbreaks in other parts of the country. In each case the mysterious malady broke out exactly twelve days after the appearance of the violet vapour. In all cases the symptoms were precisely alike, and the percentage of deaths was appalling. Neither remedy nor palliative could be devised, and the best medical brains in the country confessed themselves baffled.By this time there was no room for doubt that the terror was the deliberate work of some human fiend who had won a frightful secret from Nature’s great laboratory. But who could it be, and what possible object could he have?Leading scientific men of all nations poured in to England to help. For it was now recognised that civilisation as a whole was menaced; the fate of England to-day might be the fate of any other nation to-morrow. France and the United States sent important missions; even Russia and Germany were represented by famous bacteriologists and health experts. International jealousies and rivalries appeared to be laid aside, and even the secret service, most suspicious of rivals, began for once to co-operate and place at each other’s disposal information which might prove useful in tracking down the author of the mysterious pestilence.On the day of the meeting of the British Cabinet, two men and a pretty, dark-haired French girl were keenly discussing the terrible problem in a small but tastefully furnished flat in the Avenue Kléber, in Paris.“I know only three people in the world with brains enough to carry the thing out,” said the girl. “They are Ivan Petroff, the Russian; Paolo Caetani, the Italian, and Sebastian Gonzalez, the Spaniard. They are all three avowed anarchists, and, as we know, they are all chemists and bacteriologists of supreme ability. But I must say that there is not a scrap of evidence to connect either of them with this affair.”The speaker was Yvette Pasquet, and there was no one in whom Regnier, the astute head of the French Secret Service, placed more implicit confidence.“If the doctors could settle whether this poisoning is chemical or bacteriological it would help us a great deal,” said Dick Manton. “If it is chemical, I should be disposed to include Barakoff; he knows more about chemistry than all the others put together. But in any case, there is as yet nothing we can even begin to work on.”A fortnight went past. The death-roll in England had assumed terrible proportions, and apparently the authorities were as far off as ever from coming to grips with the mystery. But a clue came through the heroism of a London policeman.One night Constable Jervis was patrolling a beat which led him through some tumbledown streets in the lowest quarter of Canning Town. Suddenly he caught sight of a man rushing from a small empty house. At once Jervis started in pursuit of the man, who was running hard away from him. As he did so, there came the sound of an explosion, and the house the man had just left collapsed like a pack of cards. At the same time the odour of the dreaded violet vapour completely filled the narrow street.The Terror had attacked London, and Jervis knew that to cross that zone of vapour meant certain death.He did not hesitate. Muffling his face with his pocket handkerchief as he ran, he dashed at full speed after the stranger, whom he could just discern. He crossed the zone of death, almost overpowered by the curious scent of petrol and musk that loaded the still air, and a moment later was in pursuit, blowing his whistle loudly as he ran. A moment later a second policeman, hearing his colleague’s whistle, stood at the end of the road barring the way. The desperado was trapped.Snatching out a revolver, the man backed against the wall and opened fire on his pursuers who were rapidly closing in on him. But both the policemen were armed, and both opened fire. Jervis’s second shot killed the man on the spot.He proved to be a well-known member of a Russian anarchist group which had its head-quarters in the slums of Soho. The gallant Jervis had faced certain death—as a matter of fact he was among the hundred or so victims when the epidemic broke out twelve days later—but he had done his duty in accordance with the splendid traditions of the force to which he belonged.The source of the mysterious epidemic was now, to a certain extent, localised. It needed no great acumen to guess the motive and origin of the fiendish plot. But to discover the master-mind which held the full solution of the mystery was another matter.The first step was a general round-up of known members of the Anarchist Party. They were arrested by dozens, and very soon practically all who were known were under lock and key.To the intense surprise of the police, one and all acknowledged that they were fully familiar with the scheme. Many of them had actually taken part in its execution. The secret had been well kept!The explosions, it was learned, were caused by small bombs about the size of an orange. These were placed in the selected houses and timed to explode in a few hours. Evidently there was some defect in the mechanism of the one sent to Canning Town, and the man who placed it there must have seen that it was likely to explode prematurely and rushed in panic from the house.But of the source of the bombs one and all of the men professed complete ignorance. They were, it was asserted, received by post from different places on the Continent. It was evident that the crafty scoundrel at the head of the terrible organisation took elaborate precautions to prevent their sources of origin being discovered.But to have traced the outbreak to Anarchist sources was a step of the first importance. Immediately every branch of the secret service of the western world was concentrated on the problem.A hint from one of the men captured, who collapsed under the cross-examination to which the known leaders were subjected, put the police in possession of one of the bombs. It had arrived by post the day before, and the miscreant to whom it was sent was caught before he had time to make use of it.It was now possible to prove definitely that the disease caused by the bombs was chemical in its origin. Upon analysis the powder with which the bomb was filled was found to consist of a series of, apparently, quite harmless chemicals. A small portion fired by the detonator found in the bomb gave off dense clouds of the pale-violet vapour, and animals exposed to it were speedily killed, exhibiting every symptom of the terrible disease. Unhappily the secret of the detonator used defied discovery. The one found in the bomb had been used in the only experiment that had been made, and too late it was discovered that no fulminating material known would explode the apparently harmless powder.“That seems to narrow it down to Barakoff,” said Dick Manton a few days later when Regnier brought them the news. “I don’t think either of the others is equal to research work capable of producing such results. Do you know where Barakoff is now?” he asked in French.Regnier shook his head.“He was in Moscow a year ago,” he replied, “and after that we heard of him in Prague, in Rome, and lastly in Madrid, but he disappeared suddenly and we have not been able to pick up his tracks again. He is a short, powerful, thickset man with a rather hunched back, but nothing else peculiar about his appearance.”Next day, however, Regnier came to the adventurous trio in great excitement.“Barakoff is in England!” he declared. “We have just had word from Gaston Meunier who saw him in Brighton a week ago!”“But how on earth did he get there?” asked Jules. “You know every one has been looking for him for months past. He could not possibly have got through by any of the ordinary routes.”“I’m as puzzled as you are, monsieur,” was Regnier’s reply.“Well, if he is there we’d better go over,” said Dick. “Yvette can go with me in Mohawk II and Jules by the night boat. I shall fly the Mohawk to my old shed in Norfolk; I have kept it on in case of emergency, and it is quite safe.”An hour later Dick was in close talk with a young Russian named Nicholas Fedoroff. He had been an active member of a circle of dangerous anarchists in Zurich, but had dropped out and was now living in Paris. By good fortune Dick had saved his baby girl, at imminent risk of his own life, from being killed by a motor-van in Paris, hence Fedoroff was impulsively grateful.“Look here, Nicholas,” said Dick bluntly. “I want you to tell me anything you can about Barakoff.”They were seated in a small café in the Rue Caumartin, which was Fedoroff’s favourite haunt. The Russian glanced round fearfully.“Hush!” he said in broken French and in evident horror. “I—I can’t tell you! He has agents everywhere. If I were heard even speaking his name I should never get home.”The man’s agitation was so pronounced that one or two men in the café glanced at him curiously. Dick saw that the mere mention of Barakoff’s name had thrown the Russian completely off his balance.“Come to my flat,” he said quietly, “you have got to tell me.”They drove in a taxi to Dick’s flat, where a stiff dose of brandy pulled the Russian together. Yet he still trembled like a leaf.“How did you know that I knew Barakoff?” he asked.Instantly Dick was keenly on the alert. He had no idea that Fedoroff had been associated with the notorious criminal; his appeal to Fedoroff had been a chance shot. Evidently he had stumbled on a matter of importance. But he was quick to take advantage of his good luck.“Never mind how,” he said. “I do know, and that’s enough. You have got to tell me. I believe Barakoff is at the bottom of the trouble in England. I know he is there, and I want to know where he is and how he got there.”The Russian’s agitation increased.“You must not ask me; I cannot tell you,” he gasped.“Then a few words from me in a certain quarter—not the police,” Dick suggested.The Russian collapsed.“No, no, I will tell you,” he moaned. “He is in England, but I don’t know where. He flew over.”“Flew over!” echoed Dick in utter amazement. “Nonsense, he couldn’t have got in that way. Every aerodrome in England has been watched for months.”“But he did,” the Russian asserted. “He has his own aeroplane. It makes no noise, and it goes straight up and down.”Here was a surprise indeed! The secret of the helicopter with its almost unlimited power for evil was also in the hands of one of the most desperate ruffians in the world! There was indeed no time to be lost.Fedoroff could tell Dick little more. What the secret of Barakoff’s influence over him was Dick could not fathom. He would say nothing, but evidently was in deadly fear.One little item Dick did indeed extract and it was to prove valuable. Fedoroff knew that Barakoff had associates in Soho. And that was the only clue they could gain to his possible whereabouts.That evening Dick, Yvette, and Jules crossed to England, and with official introductions from Regnier, Dick lost no time in getting into communication with Detective Inspector Buckhurst, one of the ablest men of Scotland Yard’s famous “Special Department,” a man whose knowledge of the alien scum which infested London was unrivalled. To him Dick told all he knew.Buckhurst looked grave.“I know of the man, of course,” he said, “but I have never seen him and I don’t think any of my men have. We have combed Soho out pretty thoroughly, but no one answering to Barakoff’s description has been seen.”The position was very grave. If Fedoroff’s information was correct—and Dick saw no reason to doubt it—here was a desperate scoundrel lurking in England armed with an aeroplane of unknown design and power, and in possession of a terrible secret which, unless his career was brought to an end, threatened the entire population of the country. But where was he hiding, and, above all, where was his machine? Could it possibly be hidden, Dick wondered, in the very heart of London? The idea was almost incredible, but Dick knew Barakoff’s undoubted genius and his amazing daring.A remarkable feature of Yvette’s personality was her wonderful influence over children. They seemed literally to worship her. She would get into conversation with the half-tamedgaminsof the streets and in a few hours they would be her devoted slaves. She now proceeded to enlist the ragged battalions of Soho in a fashion that caused Buckhurst much amusement.“Find out for me all the hunchbacked men you can,” was all the instructions she gave them.“But, mademoiselle,” said Inspector Buckhurst, “it will be the talk of Soho, and our man if he is there will slip away.”Yvette was unmoved.“Just think a minute,” she said. “Who can go about all day and all night without being suspected? The children. Who can go into dens where your men hardly dare to venture? The children. Who know all the hidden haunts of which your men are utterly ignorant? The children. And finally, who are the most secretive people in the world? Again the children. Do not fear, Monsieur Buckhurst, they will not talk except among themselves, and that will do no harm.”Buckhurst was far from satisfied, but he had gained such a respect for Yvette that he did not venture to override her. At the same time, he told her plainly that he should keep his own men busy. Yvette only laughed.During the next forty-eight hours dozens of hunchbacked men were reported. Many of them were people whom not even the police knew. They were, of course, mostly harmless, but Buckhurst opened his eyes when one of them proved to be a notorious forger for whom the police had been looking for some months, and who had all the time been hidden under their very noses! Buckhurst began to feel a growing respect for the amazing French girl, who had beaten his smartest detectives on their own ground. But, unfortunately, none of the hunchbacks was the man they wanted, and at last they began to suspect that Fedoroff’s information was at fault.Then came a dramatic surprise. One of Yvette’s small assistants, a sharp little Polish Jew boy, came to her with a strange story. He had been wandering about the night before and had seen a hunchbacked man let himself out of the side door of a big building half-way between Greek Street and War dour Street. The man had walked a considerable distance in a northerly direction into a part of London the boy did not know at all, and had entered an unoccupied house, stayed a few minutes, and come out again. The lad had shadowed him all the way, and had followed him homewards, until he again entered the building in Soho.Dick, Jules, and Yvette turned out at once. The boy pointed out the building to them. It was a tall structure which dominated all the others in the vicinity. It was apparently a big shop with storerooms above. On the facia over the windows was the name “Marcel Deloitte, Antique Furniture.” There was nothing to indicate that it differed in the slightest degree from dozens of other shops and buildings in the neighbourhood. Yet Dick felt suspicious.“We can do nothing till I get the Mohawk handy,” said Dick. “I will bring her down to-night.”And he paused.“I wish you would keep out of this, Yvette,” he went on wistfully. “It is going to be very dangerous, I am convinced.” The French girl was growing very dear to him, and he shuddered at the idea of her being mixed up in the coming struggle with a desperado of Barakoff’s type.But Yvette shook her head.“I’m in this to the finish, Dick,” was all she said in her pretty broken English, and Dick knew he could not move her. But he was full of fear.That afternoon another explosion of the pale-violet vapour occurred in North London not far from Finsbury Park Station. Dick rushed to the spot with the boy who had followed the hunchbacked man, and the lad recognised the place without hesitation. The house destroyed was, he was confident, the one the hunchback had entered the night before.Barakoff was located at last! But how was he to be captured? The problem was not so easy.It was vital that, if possible, he should be taken alive. They knew what would follow the explosion at Finsbury Park, and there was a chance at least that if Barakoff were captured the secret of the disease, and possibly the antidote, might be wrung from him. If they could succeed in that hundreds of lives would be saved.Together the three worked out a careful plan for thecoupthey intended to bring off next morning.Very early a dozen street arabs were playing innocently close to the two entrances of the mysterious building. They were chosen specimens of Yvette’s band of ragamuffin detectives, and she knew that if Barakoff tried to escape he would have no chance of eluding their keen eyes. All the approaches were blocked by detectives, but Yvette insisted that none should approach the house itself. It was essential to the success of their plan that Barakoff’s suspicions should not be aroused.From the roof of a big building half a mile away, Dick made a careful examination of what he was now convinced was Barakoff’s hiding-place. But he could see little. The roof was flat, but it was surrounded by a parapet practically breast high. There was obviously plenty of room to conceal a small aeroplane, but Dick could see nothing.Dick and Buckhurst together saw the proprietor of the building from which Dick had made his observations. He readily consented to Dick’s plan, and towards evening placed a trusty commissionaire at the foot of the flight of steps leading to the roof with instructions that no one was to pass on any account whatever. Soon after dark the Mohawk dropped silently on to the flat roof. They were ready now to catch their bird!In the morning Yvette, under the pretence of wishing to buy some old furniture, entered the shop. So far as she could see there was nothing suspicious. There was a manager, evidently a Russian, and two assistants.Asking for a Jacobean chest which she did not see in the shop, Yvette was at length invited to the upper floors. These she found to be full of furniture.Climbing the stairs to the third floor, accompanied by the manager, Yvette found herself in a large room divided in the centre by a wall, and with a door in the middle. Opening this door the manager bowed to her to precede him, and Yvette, quite unsuspectingly, obeyed. Next second the door crashed to, and she heard a key turn in the lock. She was trapped!Before she could recover from her astonishment there was a rush of feet behind her, and she found herself seized in a grip which, as she at once recognised, it was far beyond her strength to shake off. She struggled frantically, but in vain. She was hopelessly overpowered and swiftly bound, and laid, gagged and helpless, on a sofa in the corner of the room. Then for the first time she caught sight of her captor. She recognised him at once. It was Barakoff himself!Worse still, he knew her!The man was mad with rage, his face convulsed and his eyes blazing with fury.“So, Mademoiselle Pasquet! We meet at last!” he snarled, stooping over her until his face was within a foot of her own and she could feel his hot breath upon her cheek. “But it is for the first—and last time!”Accustomed as she was to danger in many forms, Yvette could not repress a shudder. In the power of a ruffian like Barakoff! She knew, of course, that at any moment Jules might become suspicious of her long absence and come in search of her. But how long would he be and what might happen in the meantime?Barakoff set swiftly to work and fixed inside the doors heavy bars which, as Yvette realised with a sinking heart, would effectually shut out anyone trying to gain admittance, until either the door was reduced to splinters or a hole was knocked in the wall. Then he picked her up without an effort and carried her into the adjoining room. This, to Yvette’s intense surprise, was elaborately fitted up as a chemical laboratory, with all kinds of strange instruments and apparatus. It was evident that it had long been used for this purpose.With an evil sneer Barakoff took from a cupboard what Yvette had no difficulty in recognising as one of the poison bombs! This he placed on a table and attached to it a short length of fuse. Then he began to busy himself with what seemed to be preparations for leaving, packing a few articles of clothing in a small bag and laying it down with a heavy coat beside it.“When night comes, I go,” he said. “But you—you will remain. But I shall leave you in good company, mademoiselle,” and he pointed to the deadly bomb. “You will not feel dull. And after I am gone you will die—very slowly—of the twisted arms.”For a few minutes the miscreant sat silent, smoking a cigarette and regarding Yvette with a look of triumph she found even harder to bear than the consciousness of her terrible danger.Jules, on watch below, had at length become uneasy. He entered the shop and asked one of the assistants if the lady was still there.“Yes,” replied the fellow readily, “she is upstairs with the manager looking at some furniture.”Jules, his hand on his pistol in his pocket, and feeling strangely uneasy, started up the stairs. There was no one in the building. What could have become of Yvette and the manager?On the third floor he noticed the door through which Yvette had gone. He seized the handle and tried to open it. But the door was locked and there was no key.Not daring to raise an alarm for fear of the consequences to Yvette, Jules hastened down the stairs, and signalled to one of the Scotland Yard men. In a low voice Jules told him what had happened.“We must be ready to break down that door at once,” he said.With swift efficiency help was summoned, including a couple of men of the salvage corps, armed with powerful axes which would make short work of any ordinary door.While the shop assistants were kept under surveillance, Jules and his helpers mounted to the third floor. They tried the door, and knocked. There was no reply, but inside they heard the hasty scurry of feet.“Break it down,” said Inspector Buckhurst, who had been one of the first to arrive.The salvage men sprang forward, and one on each side of the door began a furious attack with their axes.Instantly a shot rang out. Splinters flew in showers, but the door, heavily barred and plated with iron, for a time defied all their efforts. At last it gave way, and headed by Jules the police party rushed in.Their first discovery was Yvette, lying unconscious and bleeding profusely from a wound in the shoulder. Barakoff had fired at her as he hurried from the room when the thunderous attack on the door began. But in his blind haste his aim had been bad, even at such short range, and she escaped with comparatively slight injury.But where was Barakoff?Rushing out on to the flat roof Jules looked hurriedly round. To the southward a queer-looking aeroplane was just vanishing into the thin mist. But behind it, going “all out,” sped the Mohawk in furious pursuit. Dick Manton was taking a hand in the game of which he was a master! There could be but one end to that, Jules thought, with a sigh of relief as he turned to look after Yvette.She was recovering consciousness and they were just about to carry her out, when one of the policemen with a loud cry dashed to the table. He had caught sight of a thin thread of smoke rising from the fuse of the bomb!Luckily he was an old bombing instructor and knew what to do. A moment later the fuse was cut and the bomb’s detonator removed. It was harmless now. Half a minute later it would have exploded.Watching keenly from his roof Dick Manton had seen Barakoff’s aeroplane rise swiftly and silently into the air. He had some slight trouble in starting the Mohawk, and the Russian was a mile away before the Englishman had started in pursuit.Crouched in the driving seat of the Mohawk, Dick kept his eyes glued on the machine in front. He soon realised, to his dismay, that the Russian machine was much the faster and was leaving him behind. By the time they had gone ten miles and were out over the open country, he could only just discern the fugitive as a mere speck in the distance, and he realised with a sinking heart that a fleck of mist would enable Barakoff to escape.Suddenly he discovered that the Russian machine had descended very low. A moment later it appeared to rise vertically, going up to a great height.Instantly Dick followed and to his surprise found himself gaining rapidly. Then the Russian seemed to slip ahead again.Several times this was repeated, and Dick at length divined the reason. The Russian could not run his elevating and driving propellers simultaneously. He travelled in a series of swoops, coming down very slowly as the machine drove forward, and then being compelled to stop the driving propellers while he gained the necessary height to continue his flight. No doubt this was explained by the fact that the planes were too small to keep the machine up without the elevating propellers.Dick saw that he held a big advantage. The Mohawk, though slightly slower, could rise and go forward at the same time under the influence of both propellers.As they sped over Kent, Dick began to realise with joy that he was gaining. Slowly the poison-fiend began to come back to him.Then came the critical moment. Five hundred yards ahead and a thousand feet below, Barakoff, close to the ground, must rise soon to gain the elevation he required.That was the moment for which Dick had been waiting. He called on his machine for the last ounce of effort he had been holding in reserve.The Mohawk shot forward. A few seconds later Dick was directly above the Russian. So far as air tactics went he had won; the Russian was entirely at his mercy.Then began surely the strangest aerial combat ever witnessed. To and fro the machines dodged, Barakoff striving to gain height and succeeding for a moment only to find his pursuer above him again and bullets whining round him; Dick striving to force the Russian down to the ground where he must either land or crash. For fully half an hour the machines flitted backwards and forwards around the town of Ashford. Dick had no fear of the result; his only risk was whether he could send Barakoff down before dusk came. Unless he could do this there was every danger that the Russian would escape under cover of darkness.At last the end came.Dick had forced his antagonist so low that, as a last desperate resort, Barakoff had to leap upward to clear a big group of elms. He miscalculated by a few feet, his machine touched the upper branches and went smashing to earth. Three minutes later Dick was standing beside the body of the death-dealer.Barakoff’s machine was a complete wreck and was blazing furiously. The man himself had been flung clear and lay in a crumpled heap, stone dead.There is little more to tell.The formula for the powder with which the bomb was charged was found in Barakoff’s laboratory, and with it, in Russian, a prescription which, on being tested, proved to be a complete cure for the disease. It was found just in time to save those who would otherwise have been the victims of the explosion at Finsbury Park.It was evident that Barakoff must have maintained his laboratory in Soho for months. Obviously the manager of the shop was one of his accomplices, and apparently he had recognised Yvette and deliberately thrown her into Barakoff’s hands. Then realising that discovery was inevitable he had slipped out of the building, probably by a window as neither of the assistants had noticed him leave. He was never found. The assistants themselves proved to be respectable young fellows who had been employed only a few weeks and who clearly knew nothing of the nefarious conspiracy.Nothing but the Mohawk had prevented Barakoff’s escape! And Dick Manton received later on the official thanks of the British Government for his daring exploit.

“Unless we can solve this terrible mystery in the course of a few weeks, it is hardly too much to say that England is doomed.”

The speaker was the white-haired Professor Durward, the distinguished head of the Royal Society. He sat facing the Prime Minister in the latter’s room at 10, Downing Street. Round the long table were grouped the members of the Cabinet. They were men who had lived through stormy and troublous times and had met stories of disaster without flinching. But, as they admitted afterwards, none of the terrible tidings of past years, when the fortunes of the Empire seemed to be tottering, had affected them to the same extent as the few brief words with which the distinguished savant summed up the long deliberations on which they had been engaged. They seemed pregnant with the very message of Fate. Almost they could see the writing on the wall.

“But, Professor,” asked the Premier, “do you really mean that nothing whatever can be done to check or prevent this terrible malady?”

“Nothing, so far as I am aware,” was the reply. “As you know the most distinguished men of science in England have been at work on the problem. We had a very full meeting last night, and the unanimous verdict was that the disease was not only absolutely incurable, but that nothing we have tried seems capable of affording even the slightest alleviation. The deaths reported already amount to nearly half a million; though the truth is being carefully concealed from the public in order to allay panic, yet practically every community in which the disease has appeared has been virtually wiped out. Curiously enough it does not seem to be spread by contagion. In spite of the rush of terrified people from districts in which it has appeared, no cases have shown themselves except in towns or villages where the mysterious violet cloud has been observed. That phenomenon has been the precursor of every outbreak.”

A month before, in the tiny village of Moorcrest, buried in the recesses of the Chilterns, an unoccupied house had suddenly collapsed with a slight explosion. No one was in the house at the time, and no one was injured. As to the cause of the explosion no one could form an idea. Nothing in the nature of the remains of a bomb could be discovered, and there was no gas laid on in the village.

But the few villagers who were about at the time spoke of seeing a dense cloud of pale violet vapour pouring from the ruins. On this point all observers were agreed, and they all agreed, too, that the cloud was accompanied by a powerful smell which strongly resembled a combination of petrol and musk. That was all the evidence that could be collected. No harm seemed to follow and the matter was speedily forgotten.

Very soon, however, the incident took on a new and sinister significance.

A week later a similar explosion took place in Ancoats, a poor and densely crowded suburb of Manchester. In every respect this incident duplicated the happening at Moorcrest. Naturally, it created something of a sensation, and the papers, recalling the Moorcrest mystery, made the most of it.

During the next fortnight similar explosions, all bearing the same distinguishing features, occurred in various parts of England. Sometimes there would be three or four in a single day in the same, or closely adjoining, areas. The public became excited. Not a single person was injured, the damage done was apparently trifling, since all the houses destroyed were of the poorest class. It looked like the work of a maniac—purposeless and without the slightest trace of a motive. People spoke of Bolshevists and Communists. But what Bolshevik or Communist, others asked, would waste time and effort to inflict such absurd pinpricks on Society?

They were soon to be undeceived. An enemy of Society was indeed at work armed with a weapon of a potency which far outstripped the paltry efforts of the Terrorists of old, to whom the bomb and the revolver were the means of world regeneration.

The explosion at Moorcrest took place on May 2nd.

Twelve days later, on May 14th, Doctor Clare-Royden, who was in practice at Little Molton, a village about four miles from Moorcrest, received an urgent message from an old patient summoning him to Moorcrest.

Doctor Royden, jumping on his motor-bicycle, answered the summons at once. A terrible surprise awaited him.

Practically every inhabitant of the village, about a hundred people in all, were in the grip of a fearful and, so far as Doctor Royden’s knowledge went, wholly unknown malady.

Its principal symptoms were complete paralysis of the arms which were strained and twisted in a terrible manner, fever which mounted at a furious speed, and agonising pains in the head. Many of the victims were alreadyin extremis, several died even while the doctor was examining them, and in the course of a few hours practically everyone attacked by the disease had succumbed. The only ones to recover were a few children, too young to give any useful information.

It would be useless to trace or describe the excitement which followed, even though the Press, at the instigation of the Government, was silent upon the matter. Help was rushed to Moorcrest, the dead were interred and the living helped in every way. The Ministry of Health sent down its most famous experts to investigate. One and all admitted that they were completely baffled.

On May 21st Ancoats was the scene of an appalling outbreak of the disease. People in the densely packed areas died like flies. But there were some remarkable circumstances which drew the attention of the trained observers who rushed to the spot to inquire into the phenomenon.

Ancoats had been the scene of the second explosion twelve days before. It was not long before a health official noticed the coincidence that the outbreaks at Moorcrest and Ancoats occurred exactly twelve days after the explosions in each place.

The coincidence was, of course, remarked upon as somewhat suspicious, but it was not until it was reproduced in the terrible outbreak at Nottingham that suspicion became a practical certainty. It was speedily confirmed by repeated outbreaks in other parts of the country. In each case the mysterious malady broke out exactly twelve days after the appearance of the violet vapour. In all cases the symptoms were precisely alike, and the percentage of deaths was appalling. Neither remedy nor palliative could be devised, and the best medical brains in the country confessed themselves baffled.

By this time there was no room for doubt that the terror was the deliberate work of some human fiend who had won a frightful secret from Nature’s great laboratory. But who could it be, and what possible object could he have?

Leading scientific men of all nations poured in to England to help. For it was now recognised that civilisation as a whole was menaced; the fate of England to-day might be the fate of any other nation to-morrow. France and the United States sent important missions; even Russia and Germany were represented by famous bacteriologists and health experts. International jealousies and rivalries appeared to be laid aside, and even the secret service, most suspicious of rivals, began for once to co-operate and place at each other’s disposal information which might prove useful in tracking down the author of the mysterious pestilence.

On the day of the meeting of the British Cabinet, two men and a pretty, dark-haired French girl were keenly discussing the terrible problem in a small but tastefully furnished flat in the Avenue Kléber, in Paris.

“I know only three people in the world with brains enough to carry the thing out,” said the girl. “They are Ivan Petroff, the Russian; Paolo Caetani, the Italian, and Sebastian Gonzalez, the Spaniard. They are all three avowed anarchists, and, as we know, they are all chemists and bacteriologists of supreme ability. But I must say that there is not a scrap of evidence to connect either of them with this affair.”

The speaker was Yvette Pasquet, and there was no one in whom Regnier, the astute head of the French Secret Service, placed more implicit confidence.

“If the doctors could settle whether this poisoning is chemical or bacteriological it would help us a great deal,” said Dick Manton. “If it is chemical, I should be disposed to include Barakoff; he knows more about chemistry than all the others put together. But in any case, there is as yet nothing we can even begin to work on.”

A fortnight went past. The death-roll in England had assumed terrible proportions, and apparently the authorities were as far off as ever from coming to grips with the mystery. But a clue came through the heroism of a London policeman.

One night Constable Jervis was patrolling a beat which led him through some tumbledown streets in the lowest quarter of Canning Town. Suddenly he caught sight of a man rushing from a small empty house. At once Jervis started in pursuit of the man, who was running hard away from him. As he did so, there came the sound of an explosion, and the house the man had just left collapsed like a pack of cards. At the same time the odour of the dreaded violet vapour completely filled the narrow street.

The Terror had attacked London, and Jervis knew that to cross that zone of vapour meant certain death.

He did not hesitate. Muffling his face with his pocket handkerchief as he ran, he dashed at full speed after the stranger, whom he could just discern. He crossed the zone of death, almost overpowered by the curious scent of petrol and musk that loaded the still air, and a moment later was in pursuit, blowing his whistle loudly as he ran. A moment later a second policeman, hearing his colleague’s whistle, stood at the end of the road barring the way. The desperado was trapped.

Snatching out a revolver, the man backed against the wall and opened fire on his pursuers who were rapidly closing in on him. But both the policemen were armed, and both opened fire. Jervis’s second shot killed the man on the spot.

He proved to be a well-known member of a Russian anarchist group which had its head-quarters in the slums of Soho. The gallant Jervis had faced certain death—as a matter of fact he was among the hundred or so victims when the epidemic broke out twelve days later—but he had done his duty in accordance with the splendid traditions of the force to which he belonged.

The source of the mysterious epidemic was now, to a certain extent, localised. It needed no great acumen to guess the motive and origin of the fiendish plot. But to discover the master-mind which held the full solution of the mystery was another matter.

The first step was a general round-up of known members of the Anarchist Party. They were arrested by dozens, and very soon practically all who were known were under lock and key.

To the intense surprise of the police, one and all acknowledged that they were fully familiar with the scheme. Many of them had actually taken part in its execution. The secret had been well kept!

The explosions, it was learned, were caused by small bombs about the size of an orange. These were placed in the selected houses and timed to explode in a few hours. Evidently there was some defect in the mechanism of the one sent to Canning Town, and the man who placed it there must have seen that it was likely to explode prematurely and rushed in panic from the house.

But of the source of the bombs one and all of the men professed complete ignorance. They were, it was asserted, received by post from different places on the Continent. It was evident that the crafty scoundrel at the head of the terrible organisation took elaborate precautions to prevent their sources of origin being discovered.

But to have traced the outbreak to Anarchist sources was a step of the first importance. Immediately every branch of the secret service of the western world was concentrated on the problem.

A hint from one of the men captured, who collapsed under the cross-examination to which the known leaders were subjected, put the police in possession of one of the bombs. It had arrived by post the day before, and the miscreant to whom it was sent was caught before he had time to make use of it.

It was now possible to prove definitely that the disease caused by the bombs was chemical in its origin. Upon analysis the powder with which the bomb was filled was found to consist of a series of, apparently, quite harmless chemicals. A small portion fired by the detonator found in the bomb gave off dense clouds of the pale-violet vapour, and animals exposed to it were speedily killed, exhibiting every symptom of the terrible disease. Unhappily the secret of the detonator used defied discovery. The one found in the bomb had been used in the only experiment that had been made, and too late it was discovered that no fulminating material known would explode the apparently harmless powder.

“That seems to narrow it down to Barakoff,” said Dick Manton a few days later when Regnier brought them the news. “I don’t think either of the others is equal to research work capable of producing such results. Do you know where Barakoff is now?” he asked in French.

Regnier shook his head.

“He was in Moscow a year ago,” he replied, “and after that we heard of him in Prague, in Rome, and lastly in Madrid, but he disappeared suddenly and we have not been able to pick up his tracks again. He is a short, powerful, thickset man with a rather hunched back, but nothing else peculiar about his appearance.”

Next day, however, Regnier came to the adventurous trio in great excitement.

“Barakoff is in England!” he declared. “We have just had word from Gaston Meunier who saw him in Brighton a week ago!”

“But how on earth did he get there?” asked Jules. “You know every one has been looking for him for months past. He could not possibly have got through by any of the ordinary routes.”

“I’m as puzzled as you are, monsieur,” was Regnier’s reply.

“Well, if he is there we’d better go over,” said Dick. “Yvette can go with me in Mohawk II and Jules by the night boat. I shall fly the Mohawk to my old shed in Norfolk; I have kept it on in case of emergency, and it is quite safe.”

An hour later Dick was in close talk with a young Russian named Nicholas Fedoroff. He had been an active member of a circle of dangerous anarchists in Zurich, but had dropped out and was now living in Paris. By good fortune Dick had saved his baby girl, at imminent risk of his own life, from being killed by a motor-van in Paris, hence Fedoroff was impulsively grateful.

“Look here, Nicholas,” said Dick bluntly. “I want you to tell me anything you can about Barakoff.”

They were seated in a small café in the Rue Caumartin, which was Fedoroff’s favourite haunt. The Russian glanced round fearfully.

“Hush!” he said in broken French and in evident horror. “I—I can’t tell you! He has agents everywhere. If I were heard even speaking his name I should never get home.”

The man’s agitation was so pronounced that one or two men in the café glanced at him curiously. Dick saw that the mere mention of Barakoff’s name had thrown the Russian completely off his balance.

“Come to my flat,” he said quietly, “you have got to tell me.”

They drove in a taxi to Dick’s flat, where a stiff dose of brandy pulled the Russian together. Yet he still trembled like a leaf.

“How did you know that I knew Barakoff?” he asked.

Instantly Dick was keenly on the alert. He had no idea that Fedoroff had been associated with the notorious criminal; his appeal to Fedoroff had been a chance shot. Evidently he had stumbled on a matter of importance. But he was quick to take advantage of his good luck.

“Never mind how,” he said. “I do know, and that’s enough. You have got to tell me. I believe Barakoff is at the bottom of the trouble in England. I know he is there, and I want to know where he is and how he got there.”

The Russian’s agitation increased.

“You must not ask me; I cannot tell you,” he gasped.

“Then a few words from me in a certain quarter—not the police,” Dick suggested.

The Russian collapsed.

“No, no, I will tell you,” he moaned. “He is in England, but I don’t know where. He flew over.”

“Flew over!” echoed Dick in utter amazement. “Nonsense, he couldn’t have got in that way. Every aerodrome in England has been watched for months.”

“But he did,” the Russian asserted. “He has his own aeroplane. It makes no noise, and it goes straight up and down.”

Here was a surprise indeed! The secret of the helicopter with its almost unlimited power for evil was also in the hands of one of the most desperate ruffians in the world! There was indeed no time to be lost.

Fedoroff could tell Dick little more. What the secret of Barakoff’s influence over him was Dick could not fathom. He would say nothing, but evidently was in deadly fear.

One little item Dick did indeed extract and it was to prove valuable. Fedoroff knew that Barakoff had associates in Soho. And that was the only clue they could gain to his possible whereabouts.

That evening Dick, Yvette, and Jules crossed to England, and with official introductions from Regnier, Dick lost no time in getting into communication with Detective Inspector Buckhurst, one of the ablest men of Scotland Yard’s famous “Special Department,” a man whose knowledge of the alien scum which infested London was unrivalled. To him Dick told all he knew.

Buckhurst looked grave.

“I know of the man, of course,” he said, “but I have never seen him and I don’t think any of my men have. We have combed Soho out pretty thoroughly, but no one answering to Barakoff’s description has been seen.”

The position was very grave. If Fedoroff’s information was correct—and Dick saw no reason to doubt it—here was a desperate scoundrel lurking in England armed with an aeroplane of unknown design and power, and in possession of a terrible secret which, unless his career was brought to an end, threatened the entire population of the country. But where was he hiding, and, above all, where was his machine? Could it possibly be hidden, Dick wondered, in the very heart of London? The idea was almost incredible, but Dick knew Barakoff’s undoubted genius and his amazing daring.

A remarkable feature of Yvette’s personality was her wonderful influence over children. They seemed literally to worship her. She would get into conversation with the half-tamedgaminsof the streets and in a few hours they would be her devoted slaves. She now proceeded to enlist the ragged battalions of Soho in a fashion that caused Buckhurst much amusement.

“Find out for me all the hunchbacked men you can,” was all the instructions she gave them.

“But, mademoiselle,” said Inspector Buckhurst, “it will be the talk of Soho, and our man if he is there will slip away.”

Yvette was unmoved.

“Just think a minute,” she said. “Who can go about all day and all night without being suspected? The children. Who can go into dens where your men hardly dare to venture? The children. Who know all the hidden haunts of which your men are utterly ignorant? The children. And finally, who are the most secretive people in the world? Again the children. Do not fear, Monsieur Buckhurst, they will not talk except among themselves, and that will do no harm.”

Buckhurst was far from satisfied, but he had gained such a respect for Yvette that he did not venture to override her. At the same time, he told her plainly that he should keep his own men busy. Yvette only laughed.

During the next forty-eight hours dozens of hunchbacked men were reported. Many of them were people whom not even the police knew. They were, of course, mostly harmless, but Buckhurst opened his eyes when one of them proved to be a notorious forger for whom the police had been looking for some months, and who had all the time been hidden under their very noses! Buckhurst began to feel a growing respect for the amazing French girl, who had beaten his smartest detectives on their own ground. But, unfortunately, none of the hunchbacks was the man they wanted, and at last they began to suspect that Fedoroff’s information was at fault.

Then came a dramatic surprise. One of Yvette’s small assistants, a sharp little Polish Jew boy, came to her with a strange story. He had been wandering about the night before and had seen a hunchbacked man let himself out of the side door of a big building half-way between Greek Street and War dour Street. The man had walked a considerable distance in a northerly direction into a part of London the boy did not know at all, and had entered an unoccupied house, stayed a few minutes, and come out again. The lad had shadowed him all the way, and had followed him homewards, until he again entered the building in Soho.

Dick, Jules, and Yvette turned out at once. The boy pointed out the building to them. It was a tall structure which dominated all the others in the vicinity. It was apparently a big shop with storerooms above. On the facia over the windows was the name “Marcel Deloitte, Antique Furniture.” There was nothing to indicate that it differed in the slightest degree from dozens of other shops and buildings in the neighbourhood. Yet Dick felt suspicious.

“We can do nothing till I get the Mohawk handy,” said Dick. “I will bring her down to-night.”

And he paused.

“I wish you would keep out of this, Yvette,” he went on wistfully. “It is going to be very dangerous, I am convinced.” The French girl was growing very dear to him, and he shuddered at the idea of her being mixed up in the coming struggle with a desperado of Barakoff’s type.

But Yvette shook her head.

“I’m in this to the finish, Dick,” was all she said in her pretty broken English, and Dick knew he could not move her. But he was full of fear.

That afternoon another explosion of the pale-violet vapour occurred in North London not far from Finsbury Park Station. Dick rushed to the spot with the boy who had followed the hunchbacked man, and the lad recognised the place without hesitation. The house destroyed was, he was confident, the one the hunchback had entered the night before.

Barakoff was located at last! But how was he to be captured? The problem was not so easy.

It was vital that, if possible, he should be taken alive. They knew what would follow the explosion at Finsbury Park, and there was a chance at least that if Barakoff were captured the secret of the disease, and possibly the antidote, might be wrung from him. If they could succeed in that hundreds of lives would be saved.

Together the three worked out a careful plan for thecoupthey intended to bring off next morning.

Very early a dozen street arabs were playing innocently close to the two entrances of the mysterious building. They were chosen specimens of Yvette’s band of ragamuffin detectives, and she knew that if Barakoff tried to escape he would have no chance of eluding their keen eyes. All the approaches were blocked by detectives, but Yvette insisted that none should approach the house itself. It was essential to the success of their plan that Barakoff’s suspicions should not be aroused.

From the roof of a big building half a mile away, Dick made a careful examination of what he was now convinced was Barakoff’s hiding-place. But he could see little. The roof was flat, but it was surrounded by a parapet practically breast high. There was obviously plenty of room to conceal a small aeroplane, but Dick could see nothing.

Dick and Buckhurst together saw the proprietor of the building from which Dick had made his observations. He readily consented to Dick’s plan, and towards evening placed a trusty commissionaire at the foot of the flight of steps leading to the roof with instructions that no one was to pass on any account whatever. Soon after dark the Mohawk dropped silently on to the flat roof. They were ready now to catch their bird!

In the morning Yvette, under the pretence of wishing to buy some old furniture, entered the shop. So far as she could see there was nothing suspicious. There was a manager, evidently a Russian, and two assistants.

Asking for a Jacobean chest which she did not see in the shop, Yvette was at length invited to the upper floors. These she found to be full of furniture.

Climbing the stairs to the third floor, accompanied by the manager, Yvette found herself in a large room divided in the centre by a wall, and with a door in the middle. Opening this door the manager bowed to her to precede him, and Yvette, quite unsuspectingly, obeyed. Next second the door crashed to, and she heard a key turn in the lock. She was trapped!

Before she could recover from her astonishment there was a rush of feet behind her, and she found herself seized in a grip which, as she at once recognised, it was far beyond her strength to shake off. She struggled frantically, but in vain. She was hopelessly overpowered and swiftly bound, and laid, gagged and helpless, on a sofa in the corner of the room. Then for the first time she caught sight of her captor. She recognised him at once. It was Barakoff himself!Worse still, he knew her!

The man was mad with rage, his face convulsed and his eyes blazing with fury.

“So, Mademoiselle Pasquet! We meet at last!” he snarled, stooping over her until his face was within a foot of her own and she could feel his hot breath upon her cheek. “But it is for the first—and last time!”

Accustomed as she was to danger in many forms, Yvette could not repress a shudder. In the power of a ruffian like Barakoff! She knew, of course, that at any moment Jules might become suspicious of her long absence and come in search of her. But how long would he be and what might happen in the meantime?

Barakoff set swiftly to work and fixed inside the doors heavy bars which, as Yvette realised with a sinking heart, would effectually shut out anyone trying to gain admittance, until either the door was reduced to splinters or a hole was knocked in the wall. Then he picked her up without an effort and carried her into the adjoining room. This, to Yvette’s intense surprise, was elaborately fitted up as a chemical laboratory, with all kinds of strange instruments and apparatus. It was evident that it had long been used for this purpose.

With an evil sneer Barakoff took from a cupboard what Yvette had no difficulty in recognising as one of the poison bombs! This he placed on a table and attached to it a short length of fuse. Then he began to busy himself with what seemed to be preparations for leaving, packing a few articles of clothing in a small bag and laying it down with a heavy coat beside it.

“When night comes, I go,” he said. “But you—you will remain. But I shall leave you in good company, mademoiselle,” and he pointed to the deadly bomb. “You will not feel dull. And after I am gone you will die—very slowly—of the twisted arms.”

For a few minutes the miscreant sat silent, smoking a cigarette and regarding Yvette with a look of triumph she found even harder to bear than the consciousness of her terrible danger.

Jules, on watch below, had at length become uneasy. He entered the shop and asked one of the assistants if the lady was still there.

“Yes,” replied the fellow readily, “she is upstairs with the manager looking at some furniture.”

Jules, his hand on his pistol in his pocket, and feeling strangely uneasy, started up the stairs. There was no one in the building. What could have become of Yvette and the manager?

On the third floor he noticed the door through which Yvette had gone. He seized the handle and tried to open it. But the door was locked and there was no key.

Not daring to raise an alarm for fear of the consequences to Yvette, Jules hastened down the stairs, and signalled to one of the Scotland Yard men. In a low voice Jules told him what had happened.

“We must be ready to break down that door at once,” he said.

With swift efficiency help was summoned, including a couple of men of the salvage corps, armed with powerful axes which would make short work of any ordinary door.

While the shop assistants were kept under surveillance, Jules and his helpers mounted to the third floor. They tried the door, and knocked. There was no reply, but inside they heard the hasty scurry of feet.

“Break it down,” said Inspector Buckhurst, who had been one of the first to arrive.

The salvage men sprang forward, and one on each side of the door began a furious attack with their axes.

Instantly a shot rang out. Splinters flew in showers, but the door, heavily barred and plated with iron, for a time defied all their efforts. At last it gave way, and headed by Jules the police party rushed in.

Their first discovery was Yvette, lying unconscious and bleeding profusely from a wound in the shoulder. Barakoff had fired at her as he hurried from the room when the thunderous attack on the door began. But in his blind haste his aim had been bad, even at such short range, and she escaped with comparatively slight injury.

But where was Barakoff?

Rushing out on to the flat roof Jules looked hurriedly round. To the southward a queer-looking aeroplane was just vanishing into the thin mist. But behind it, going “all out,” sped the Mohawk in furious pursuit. Dick Manton was taking a hand in the game of which he was a master! There could be but one end to that, Jules thought, with a sigh of relief as he turned to look after Yvette.

She was recovering consciousness and they were just about to carry her out, when one of the policemen with a loud cry dashed to the table. He had caught sight of a thin thread of smoke rising from the fuse of the bomb!

Luckily he was an old bombing instructor and knew what to do. A moment later the fuse was cut and the bomb’s detonator removed. It was harmless now. Half a minute later it would have exploded.

Watching keenly from his roof Dick Manton had seen Barakoff’s aeroplane rise swiftly and silently into the air. He had some slight trouble in starting the Mohawk, and the Russian was a mile away before the Englishman had started in pursuit.

Crouched in the driving seat of the Mohawk, Dick kept his eyes glued on the machine in front. He soon realised, to his dismay, that the Russian machine was much the faster and was leaving him behind. By the time they had gone ten miles and were out over the open country, he could only just discern the fugitive as a mere speck in the distance, and he realised with a sinking heart that a fleck of mist would enable Barakoff to escape.

Suddenly he discovered that the Russian machine had descended very low. A moment later it appeared to rise vertically, going up to a great height.

Instantly Dick followed and to his surprise found himself gaining rapidly. Then the Russian seemed to slip ahead again.

Several times this was repeated, and Dick at length divined the reason. The Russian could not run his elevating and driving propellers simultaneously. He travelled in a series of swoops, coming down very slowly as the machine drove forward, and then being compelled to stop the driving propellers while he gained the necessary height to continue his flight. No doubt this was explained by the fact that the planes were too small to keep the machine up without the elevating propellers.

Dick saw that he held a big advantage. The Mohawk, though slightly slower, could rise and go forward at the same time under the influence of both propellers.

As they sped over Kent, Dick began to realise with joy that he was gaining. Slowly the poison-fiend began to come back to him.

Then came the critical moment. Five hundred yards ahead and a thousand feet below, Barakoff, close to the ground, must rise soon to gain the elevation he required.

That was the moment for which Dick had been waiting. He called on his machine for the last ounce of effort he had been holding in reserve.

The Mohawk shot forward. A few seconds later Dick was directly above the Russian. So far as air tactics went he had won; the Russian was entirely at his mercy.

Then began surely the strangest aerial combat ever witnessed. To and fro the machines dodged, Barakoff striving to gain height and succeeding for a moment only to find his pursuer above him again and bullets whining round him; Dick striving to force the Russian down to the ground where he must either land or crash. For fully half an hour the machines flitted backwards and forwards around the town of Ashford. Dick had no fear of the result; his only risk was whether he could send Barakoff down before dusk came. Unless he could do this there was every danger that the Russian would escape under cover of darkness.

At last the end came.

Dick had forced his antagonist so low that, as a last desperate resort, Barakoff had to leap upward to clear a big group of elms. He miscalculated by a few feet, his machine touched the upper branches and went smashing to earth. Three minutes later Dick was standing beside the body of the death-dealer.

Barakoff’s machine was a complete wreck and was blazing furiously. The man himself had been flung clear and lay in a crumpled heap, stone dead.

There is little more to tell.

The formula for the powder with which the bomb was charged was found in Barakoff’s laboratory, and with it, in Russian, a prescription which, on being tested, proved to be a complete cure for the disease. It was found just in time to save those who would otherwise have been the victims of the explosion at Finsbury Park.

It was evident that Barakoff must have maintained his laboratory in Soho for months. Obviously the manager of the shop was one of his accomplices, and apparently he had recognised Yvette and deliberately thrown her into Barakoff’s hands. Then realising that discovery was inevitable he had slipped out of the building, probably by a window as neither of the assistants had noticed him leave. He was never found. The assistants themselves proved to be respectable young fellows who had been employed only a few weeks and who clearly knew nothing of the nefarious conspiracy.

Nothing but the Mohawk had prevented Barakoff’s escape! And Dick Manton received later on the official thanks of the British Government for his daring exploit.

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