"H-h-help!" Tom gasped.
Moments dragged by with agonizing slowness. Tom felt as if his last ounce of breath were being squeezed out by the viselike pressure.
Suddenly a gravelly Western voice reached him, singing "Home on the Range." It drew closer, swelling into a foghorn drone as the lab door swung open.
"Good old Chow!" Tom thought. "Thank heavens!"
The grizzled, bowlegged cook ambled cheerfully into the laboratory, pushing a lunch cart. But, to Tom's dismay, he cast only a passing glance at the figure in the tank.
free
"Soup's on, son!" Chow announced loudly. He began to ladle out a bowl of oyster stew from a steaming pot. Evidently he had not realized the young inventor's dilemma!
"Extra good today too, if I do say so myself!" the old Texan went on, setting out the rest of the lunch. "Well, come on, buckaroo! Break away from them chores an' dive in! Brand my cactus salad, if there's one thing that riles a cook—"
Summoning all his strength, Tom croaked out weakly, "Chow!... Get help!"
At the strange sound of Tom's voice, Chow jerked around. His eyes bugged out at the look on the young inventor's face. Then he dashed to the public-address outlet on the wall and switched on the mike.
"Help! Help!" Chow yelled. "Tom Jr.'s trapped in his lab!"
The roly-poly chef was quivering in panic. He dashed across the room and paced helplessly about the tank. Within moments, excited men were crowding into the laboratory.
Mr. Swift, among the first to arrive, took in the situation at a glance. He dashed to the control board and slammed shut the main switch, thus cutting off power to the ion-drive jet.
"Whew! Th-thanks, Dad!" Tom's chest was heaving as he gulped in air to relieve his tortured lungs.
Tom Sr. helped him climb out of the tank.
"B-b-brand my rhubarb rockets," Chow stuttered. "What in tarnation happened?"
"Guess I gunned my new skin-diving jet a bit too hard," Tom said sheepishly. "It was almost a K.O. for me!"
Mr. Swift asked Tom about the invention. After explaining how it worked, Tom added with a grin, "Maybe you'd better hang around, Dad, until I install some sort of density-control gadget for my hydrolung. Then I can go up or down, or stay at any level easily."
Such a device, Tom felt, might prove to be a lifesaver if he should ever become trapped under water—perhaps far from help.
The elder scientist chuckled and threw an arm around Tom's shoulders. "I'd say you could design something like that with your eyes shut, son!"
Warmed by his father's appreciation, Tom set to work improving his diving apparatus.
An hour later Bud came bursting into the laboratory. "Hey! What's this I hear about your getting hammerlocked by a water jet?" the husky young pilot asked. He had been on a test flight and just returned.
Tom laughed good-naturedly. "Nothing serious. In fact, I felt pretty silly," he told his chum. "I souped up our ion-drive gizmo a bit too much."
Bud picked up the slender metal cylindrical assembly from the workbench. "This it?" he asked, his curiosity immediately aroused.
Tom nodded and demonstrated the device in the test tank.
Bud whistled with glee. "Boy! With this rig, we can scoot around like a pair of barracudas!" he exclaimed. "What about that other thing you're working on?" Bud pointed to a small electronic chassis on the workbench, studded with a tangle of transistors, diodes, and condensers.
"It's a density-control device," Tom explained. "A substitute for ballast tanks, you might say. It'll enable us to rise or sink to any depth at will, simply by varying our underwater density."
Tom said the device would be carried in a small case, hooked to the diver's belt, with a single tuning-knob control. The "throttle" or speed control for the ion drive would be housed in the same unit.
"I can't wait to try out the new diving gear," Bud said excitedly.
By four o'clock Tom had the apparatus perfected, and turned it over to Arv Hanson for fast duplication.
"We'll give it a shakedown tomorrow morning," he told Bud.
The duplicates of the ion drive and density control were ready and waiting when the boys arrived at the plant next day. They immediately flew to Fearing Island and embarked in a motor launch, with Zimby Cox again at the helm.
This time they cruised out to deeper water. Tom and Bud donned flippers and belt, and helped each other strap on his ion-drive jet.
"Downwe go, into the wilds of sharks!" Bud chortled lustily. "Watch your step, Tom."
"Just make sure you come up again in one piece," Zimby said with a grin. "Also, don't get carried away with that ion squirt gun and take off on a round-the-world underwater cruise."
"Who knows?" Tom joked. Adjusting his face mask, he plunged over the side. Bud followed.
Down they glided into the sea-green wilderness. Leveling off in sight of the ocean floor, they tried their drive jets. The effect was thrilling!Zip ... Whoosh!They darted to and fro like human torpedoes.
Then Tom twirled the control knob of his density unit. Immediately he bobbed upward like a cork. A reverse twirl sent him plummeting toward the bottom again. Bud, watching with wide-eyed excitement, began experimenting on his own.
Soon the boys were engaging in all sorts of underwater acrobatics. Presently Bud felt a nudge in the back that sent him hurtling a dozen yards through the water.
"Snuck up on me, eh, pal?" he thought with a chuckle. "Okay, Tom old boy, here's where the undersea terror strikes back!"
Swooping around to return the compliment, Bud gulped in surprise. Instead of his chum, he found himself face to face with a bottle-nosed dolphin!
"Good night!" Bud thought. "A porpoise! So you're the joker who nudged me!"
With a playful toss of its comical-looking snout, the porpoise swam off, as if inviting Bud to join in the fun and games. A whole school of the creatures cavorted into view.
"Okay! If you want to play!" Chuckling, Bud darted in pursuit, whacked the porpoise that had nudged him, and jetted off again. The porpoise gave chase, whistling and grunting audibly.
Tom joined in the fun, and soon a rollicking game of underwater tag was in full swing. The dolphins seemed as playful and mischievous as small children.
Twenty minutes later the boys surfaced and hauled themselves aboard. Both tore off their masks and flopped into the boat, shaking with laughter, surfacing and diving.
"What was so funny down there?" Zimby asked.
When Tom told him about the dolphins, he too burst into laughter. The porpoises rose into view and convoyed the launch all the way back to the island.
The boys were so jubilant over the performance of the new hydrolung gear that Tom decided to press his search for the Brungarian sea-prowlers immediately. Soon after lunch they took off in theSea Houndand headed for the South Atlantic. Hank Sterling, Chow Winkler, and two crewmen accompanied the boys.
Dazzling afternoon sunshine sparkled over the sea when they reached the missile search area. Tom immediately contacted Art Wiltessa and the task-force ships. They had no new developments to report.
The young inventor gave orders to submerge. As soon as the seacopter touched bottom, Tom and Bud swam out through the air lock with their hydrolungs.
They probed about for half an hour, ranging farther and farther from theSea Hound. Then Tom felt a touch on his arm. He turned and saw Bud pointing off excitedly to the right.
A strange submarine was moving slowly toward them!
CHAPTER VIII
DATE TROUBLE
The boys exchanged looks of fear through their face masks as the knifelike hull and conning tower of the submarine loomed gray and ghostly.
Was the sub Brungarian? And what was it up to? Were the two young skin divers about to be run down or kidnaped?
Or was its crew friendly?
"Better not chance it," Tom decided fast. He caught Bud's eye again and motioned upward with a jerk of his thumb. "Topside, pal!"
"Roger!" Bud's lips shaped the word silently behind his face mask.
In a twinkling both boys flicked their density controls and zoomed upward. The sub at once seemed to betray a hostile intent. It blew its tanks and planed upward in pursuit. But Tom and Bud easily pulled away. Their density units worked like magic, shooting them straight toward the surface.
"Wow!" Bud shoved back his face mask as they broke water. "That baby was after us and no mistake!"
Tom nodded, treading water. "Let's not stick around here, either! We'll soon have company again if we do!"
Bud did not argue. "Where to, skipper?"
In the fresh salt air, with the sunshine sparkling on the waves, it was hard to believe that an enemy submarine was hot on their trail. But both youths realized their peril was growing by the moment.
"Back toward theSea Hound," Tom said, pointing north-northwest. "Submerge as we go!"
Bud circled his thumb and forefinger, then adjusted his mask, and the two boys plunged back in. On a sloping downward course, they sped along like undersea rockets, their ion jets functioning perfectly. Minutes later, they sighted the seacopter.
Hank waved to them through the cabin window as they glided past. The air lock opened speedily and the two boys entered. Both heaved sighs of relief when they were safely inside.
"Somethin' wrong?" Chow asked, sniffing trouble.
"A strange submarine," Tom reported. "Brungarian more than likely. It may be heading this way if they've tracked us."
"A sub?" Hank was startled. "We've picked up nothing on sonar!"
"Check again," Tom ordered.
The sonarman bent to his scope and Hank listened intently over the hydrophones. Neither could detect any sign of another craft.
"Probably the same one that fired on us the last time," Tom said grimly. "We'd better clear out before they take another pot shot at us."
Hank sent theSea Houndzooming toward the surface while the boys changed quickly into slacks and T shirts. Then Tom took over the controls for the flight home.
"Brand my vitamin vittles! Are we just goin' to turn tail an' run every time them varmints come skulkin' around?" Chow fumed as the seacopter arrowed northward.
"Not if I can help it," Tom vowed. "But first I must figure out a way to make our own craft invisible, so to speak. It's the only way to protect our American crews, Chow, if we hope to do any secret digging for that lost missile."
"Want another suggestion, skipper?" Bud put in. "This one is about the hydrolung."
"Sure. Speak up."
"How about putting some sort of communications system into our hydrolung gear? If I hadn't been close enough to grab you when I spotted that sub, it might have been curtains, pal!"
"You're right," Tom agreed. "I'll get to work on it."
It was sunset when Fearing Island came into sight. The boys flew a Pigeon Special back to Enterprises, where Tom phoned a full report on the mystery sub to the Navy Department. Then the two chums drove to the Swift home for a late supper.
Phyl Newton was visiting Sandy that evening, but the girls displayed a marked coolness toward Tom and Bud. Instead of engaging in conversation, they retired to Sandy's room upstairs to play records, while Mrs. Swift served the boys a warmed-up but tasty meal of roast beef and mince pie.
"What's wrong? Are we repulsive or something?" Bud asked as they ate.
Tom shrugged, concentrating on a mouthful of roast beef. "Search me. We sure don't seem very popular with the girls tonight."
Mrs. Swift, overhearing their remarks in the kitchen, smiled but maintained a diplomatic silence.
Suddenly Bud slapped his forehead. "Good night! No wonder!"
Tom looked up with a grin of interest. "Well, what have we done?"
"It's what wehaven'tdone, pal!" Bud retorted. "We had a date this afternoon, remember? That beach party and dance put on by Sandy and Phyl's school sorority!"
Tom gulped. "Oops! Boy, we really did pull a boner this time! I completely forgot!"
As they finished supper, the boys discussed various ways to make amends. Boxes of chocolates? Flowers? None of their ideas seemed to have the proper spark.
"We'll have to come up with something super," Bud said.
"Right!" Tom agreed. "Let's sleep on it and see if we can't dream up something by tomorrow morning that'll really wow them."
The next morning Tom had a flash of inspiration as he drove to the plant in his sports car. He hailed Bud at the first opportunity.
"I have it, pal! What say we stage an old-fashioned square dance Tuesday night at the yacht club on Lake Carlopa?"
Bud's eyes lighted up. "Hey, that's a great idea! We'll invite a whole gang, get Chow to handle the refreshments, and make it a real shindig!"
The boys shook hands enthusiastically. Eager to patch matters up as soon as possible, they invited Sandy and Phyl out to lunch that day. Over dessert, the boys announced their plans for a square dance.
"We—uh—realize we goofed yesterday on that beach party," Tom said sheepishly. "But we're hoping you'll give us another chance."
The girls looked at each other, their eyes twinkling, then burst into giggles.
"You're forgiven completely!" Phyl declared.
"Then it's a date?" Bud put in.
"You bet it's a date, and don't you forget it!" Sandy warned. "Phyl and I are going right over to Dorman's Department Store and pick out some cute outfits for the dance!"
Tom and Bud chuckled over the success of their scheme as they drove back to Enterprises. Later that afternoon a telephone call interrupted Tom as he worked in his lab on a sonic-communications system for the hydrolung apparatus.
"This is Lester Morris," said the voice at the other end of the line. The name did not register with Tom at first until his caller added, "I hear you're planning a square dance Tuesday night at the yacht club."
Suddenly Tom remembered. Lester Morris was a popular dance orchestra leader in and around Shopton. He was also much in demand as a square-dance caller and fiddler.
"That's right," Tom said with a chuckle. "News must travel fast. We just phoned invitations to our friends."
Morris asked if musicians had been hired for the evening. When Tom said No, his caller volunteered for the job, offering to provide a small combo of country-style players. His asking price sounded like a bargain rate, and Tom, knowing Morris's reputation, was only too glad to engage him.
"Lucky break, his calling," the young inventor thought as he hung up.
Bud was delighted to hear of the arrangement when he came into the laboratory a while later. The boys talked over their dance plans for a few moments, then Bud asked:
"How's our underwater talkie system coming?"
Tom scratched his jaw thoughtfully. "A bit tricky but not too difficult," he replied. "It's mostly a job of adapting the sonarphone arrangement from our Fat Man suits—in miniature."
A tiny mike, Tom explained, would be installed on the inside of each face mask, with its output feeding to a sonar transducer on the exterior. The receiving transducers would feed from amplifiers to earphones. The hookup would be powered by the solar battery in the hydrolung power unit, by connecting wires through the breathing tube.
"That's neat, Tom," Bud said. "Need any help?"
"You can mold us a pair of new face masks—big enough to cover the earphones," Tom suggested. He handed Bud a penciled sketch from the workbench, adding, "Then drill the holes for the mikes and earphones—the dimensions are there on the drawing. But watch it so you don't crack the plastic."
panic
While Bud complied, Tom began assembling the tiny electronic parts. In two hours the gear was ready for testing.
Tom wiped his perspiring forehead and gave Bud a grin of satisfaction. "Go get your swim trunks, fly boy. Let's give it a tryout in the tank."
"Swell idea! Be back in a jiff!"
After a quick change, the boys strapped on the new hydrolung equipment. Before adjusting his face mask, Tom mentioned that he had inserted scrambling circuits into the communicators to foil any enemy eavesdroppers.
"If they do pick up anything, it'll sound like chop suey," Tom ended with a chuckle.
The boys submerged in the test tank and proceeded to give the new underwater communication system a thorough check-out. It worked perfectly. Ten minutes later Tom and Bud clambered out again, dripping wet but well satisfied.
They had just peeled off their masks when Chow came charging into the lab, with a crowd of workmen and technicians at his heels. The cook was wild-eyed with panic.
"What's wrong, Chow?" Tom asked in alarm.
CHAPTER IX
A MAGNETIC KIDNAPING
"The space people or some enemy's invadin' us!" Chow shouted. "Take a squint through your telescope, boss! Brand my bazooka, they may be landin' any second!"
More people came streaming in, attracted by the chef's cries and gesticulations. Some were bewildered, a few frightened. Others were laughing, thinking the whole thing a joke. The scene was rapidly taking on the proportions of a riot!
"Whoa! Slow down, Chow!" Tom ordered, trying to make himself heard above the din.
"It—it's the truth, boss!" Chow stammered, mopping his brow with a huge red bandanna. "Why, sufferin' rattlesnakes, didn't I hear 'em spoutin' their space lingo with my own ears?"
"You heardwhat?" Bud said.
"Spoutin' space talk!" the cook repeated. "It come right over the loud-speaker in the galley! They was chitter-chatterin' plottin' to blow us all to smithereens!"
"That's a fact! We heard it, too!" one of the workmen chimed in.
Tom and Bud looked at each other blankly. Then suddenly Tom's eyes kindled with a dawning suspicion. Whirling around, he rushed over to inspect the public-address outlet on the wall.
Meanwhile, Mr. Swift had just driven in through the main gate of Enterprises. "What's going on?" he asked the guard at the gate, noting the excited hubbub around Tom's laboratory.
"Don't rightly know, sir," the guard replied. "I was wondering myself. I know it sounds crazy, but I thought I heard someone yelling there was going to be a space attack."
Mr. Swift's eyebrows lifted in amazement. Without further discussion, he stepped on the accelerator and sped off along the paved drive. Seconds later, his car braked to a stop near Tom Jr.'s private laboratory. The scientist jumped out and made his way through the milling crowd.
"What's going on?" Mr. Swift stared in astonishment at Tom and Bud, who were both doubled up with laughter.
"A scrambled radio alert, Dad," Tom gasped between chuckles. "Chow thought some Martian monsters were invading us, and sort of pushed the panic button."
The Texan blushed as Tom explained what had happened. Realizing Chow's embarrassment, Tom tried to make his mistake sound understandable.
Apparently the power line to the ion-drive control board had somehow picked up the boys' scrambled conversation underwater. The signal had been transferred by inductance in the wall wiring and amplified over the public-address system.
"Our wall mike was on," Tom added, "and it probably picked up some of the sound waves from the tank. Anyhow," he concluded, slapping the cook affectionately on the back, "I'm sure glad we have a wide-awake hombre like Chow in the outfit. It wouldn't be the first time he's saved our necks!"
Chow perked up, and the employees, reassured, returned to their jobs.
"I have some news of my own," Mr. Swift announced with a smile as the room cleared. "But I'm afraid it'll sound pretty tame compared to a space attack."
"Let's hear it, Dad," Tom said eagerly.
"I've been conducting some experiments with those space plants," the elder scientist said. "It looks as though they may prove to be a valuable nutritional source."
The plants, Mr. Swift went on, showed promise of producing enormous amounts of protein quickly and cheaply—enough to increase the world's food supply by a sizable margin. Moreover, he had isolated a vitamin in this protein not found in any of man's present foods.
"Doc Simpson has been working with me," Mr. Swift concluded. "He has been doing some experiments of his own with a vitamin extract from the space plants. He thinks it may prove highly beneficial to human beings."
Tom was thrilled, and even Bud realized that Mr. Swift's cautious report could well turn out to be of history-making importance.
"I'd say your news makes a phony space attack look pretty tame, Dad," Tom said, his eyes flashing enthusiastically. "With the earth's population increasing, this could be the answer to the food problem."
"Don't tell Chow," Bud added, "or we may find spaceburgers on the next menu!"
The Swifts chuckled. Chow's hobby of concocting weird dishes was a standing joke at Enterprises, and already had led to such dubious triumphs as armadillo stew and rattlesnake soup.
Monday morning Tom buckled down seriously to the job of designing an undetectable sub. His drawing board was littered with sketches and diagrams when the phone rang, breaking in on his thoughts. Tom answered it with a scowl of impatience. The caller was Lester Morris.
"Could you meet me at the yacht club to talk over the dance program?" Morris asked.
Tom hesitated. For Sandy's and Phyl's sakes he was eager to do everything possible to make the square dance a success. But on the other hand....
"I'm pretty busy today," Tom said. "But my sister and my friend Bud Barclay can tell you what we want—probably better than I can. Suppose I ask them to meet you there after lunch?"
There was a slight pause. "Very well," Morris agreed, although he sounded a bit annoyed.
After hanging up, Tom phoned Bud and asked him to keep the appointment. Bud was only too happy to oblige, jumping at the chance to take Sandy out to lunch beforehand.
At one o'clock the husky young pilot and his date strolled into the yacht club lounge. Lester Morris was nowhere in sight, so they sat down to wait. Twenty minutes later the musician still had not appeared.
"I hope he hasn't forgotten," Sandy said, glancing at her wrist watch.
"If he's a square-dance caller, his memory ought to be extra good," Bud joked. "Fine thing if he can't even remember the time of day!"
After waiting a while longer, Bud decided to telephone Morris's home. But at that moment a thin, seedy-looking man came into the lounge. His close-set eyes and loudly striped suit combined to give him a somewhat disreputable appearance.
"Good grief! Len Unger!" Sandy whispered. "What does he want with us?"
Unger was walking straight toward them. Both Bud and Sandy had met him occasionally around town and found him obnoxious.
"Sorry, but Morris got tied up," Unger informed them. "He sent me to talk to you."
Sandy's blue eyes met Bud's in a flicker of distaste, but she tried to conceal her feelings. "Please sit down," she invited Unger politely. "What square-dance numbers does Mr. Morris do?"
Len Unger shrugged. "You name 'em."
"But, my goodness," Sandy said, puzzled, "how do we know he'll have the squares I name?"
Unger stared at her as if he did not quite understand. "You mean, can he call off the dances you want? If he can't, I'll let you know."
"Does he do patter calls or singing calls?" Bud put in.
Again Unger hesitated, then said, "Both."
"Wonderful!" Sandy exclaimed gleefully. "I thought he only did singing calls." After a moment's thought, she went on, "Well, let's see. What about 'Birdie in the Cage'?... And 'The Gal from Arkansas' ... 'Uptown and Downtown'...."
Unger jotted the names on the back of an envelope. Pausing a moment, he remarked, "Guess your brother was too busy to make it today, eh, Miss Swift? What kind of ex-spearmints is he working on now?"
"I really couldn't say," Sandy replied coldly. She always made it a point not to discuss Tom Jr.'s or her father's research work with outsiders.
Unger persisted chattily, "I read where he handled that Jupiter probe shoot for the Navy."
"Let's get back to square dancing," snapped Bud. As he and Sandy finished planning the program, Len Unger continued to drop remarks and questions about "The Great Tom Swift" and his inventions. All prying queries were side-stepped.
As soon as possible Sandy and Bud cut short the conversation and left the yacht club. Unger's face wore an angry sneer as they walked out.
"What a creep!" Bud said, when he and Sandy were driving back in his red convertible.
Meanwhile, in his private laboratory at Enterprises, Tom was somewhat discouraged. He had tried several different experimental attacks on the problem of an undetectable submarine. None had worked out successfully.
"I thought that idea of a sonar-wave baffle might lead somewhere," he murmured, "but it looks as though I'm wrong."
Flopping down on a stool at his workbench, Tom cupped his chin in his hands. He was frowning, deep in thought, as the pudgy figure of Chow Winkler came into the laboratory.
"'Smatter, boss?" the cook inquired cheerfully. "Ain't your ole think box workin' today?"
"Doesn't seem to be," Tom confessed.
"Give it time, son. Tomorrow's another day," Chow said philosophically. "What you need is a haircut for the square dance."
Tom laughed in spite of himself. "Maybe you're right, Chow. Might help me think better."
Tom got off the stool and stretched out the kinks in his legs. He strolled outside with Chow, then scootered to the parking lot and hopped into his sleek, silver sports car.
A moment later he was whizzing off in the direction of Shopton. Nearing town, Tom turned off on a side-road short cut. He noticed in his mirror that a truck behind him also turned off.
"Really barreling along!" Tom thought. "If you're in such a hurry, the road's yours, pal."
He pulled over sharply, motioning the truck to pass. Instead, to Tom's surprise, it closed in straight behind him. The next moment, Tom saw a port open below the truck's hood and a strange-looking device pop out on a springlike steel cable.
It clamped magnetically to Tom's rear bumper! His car was caught like a fish on a line!
Tom stepped on the accelerator, trying to pull free. The truck at once swerved off the road, steering around a utility pole. As the cable tautened, there was a sickening screech of metal and the sports car was brought to a crashing halt!
Tom's head slammed against the side window. With a groan, the young inventor blacked out.
CHAPTER X
TELEPHONE CODE
As he regained consciousness, Tom's eyes fluttered open. Sparks of pain shot through his head. A groan escaped his lips.
"Oo-o! What hit me?" Tom wondered.
He was lying on a sofa in a strange room. Someone was seated nearby, watching him. Tom tried to move his limbs and sit up. Then he discovered that his wrists and ankles were tied with sash cord.
"Better lie still, sonny boy," a gruff voice advised. "You ain't goin' nowhere."
The man who had spoken got up from his chair and came over to the sofa. He was of medium height, very muscular looking, with cold, glittering eyes. Rolled-up shirt sleeves revealed his powerful, hairy arms.
"Where am I?" Tom asked, suddenly remembering the events on the road before he blacked out. "And what's this all about?"
The man said with a mirthless grin, "You're a prisoner. And you're goin' to stay here until the cops let Dimitri Mirov go. It's up to you how fast they spring him."
The huge man lifted a telephone from an end table adjoining the sofa and set it on the floor alongside Tom.
"Here's a phone. Go ahead and use it, but don't try any funny stuff."
In spite of his headache, Tom's brain was racing. What to do now? He shut his eyes and screwed up his face in an expression of pain, pretending to be still groggy while he stalled for time to figure out his next move.
"How canIget Mirov out of jail?" Tom faltered.
"You figure it out!" the man snarled. "And you'd better get results if you want to stay healthy!"
Through half-slitted eyes, Tom noted the telephone number printed on the dial. Evidently his captor had not thought to remove it from the instrument. A lucky break!
If only, Tom thought, he could devise some way to transmit the number to Ames without arousing his captor's suspicion—the phone's location could then be traced!
What about some sort of double-talk code? For instance, Tom told himself, keep slipping numbers into the conversation in order to transmit the digits of the telephone number. Would Ames catch on?
The number shown was BArwick 3-7156. BA on the dial would be the same as "2, 2."
"Come on! Quit stalling!" the man said threateningly.
"How can I dial with my hands tied?" Tom objected.
"I'll do the dialing, wise guy!"
He lifted the phone from its cradle and extended it to his prisoner. Tom told him the Enterprises number, then asked for Ames's extension as the switchboard operator answered. A moment later the security chief's voice came over the line.
"Ames speaking."
"This is Tom Jr., Harlan." His captor bent close to the receiver as Tom replied, in order to overhear what was being said. "I've been thinking," the young inventor went on, "that it might be smart to have Mirov released."
"Released!" Ames gasped in surprise. "But why, skipper?"
"Well ... er ... as a good-will gesture," Tom said. "I think it might prevent future trouble with the Brungarians, don't you?"
"I do not!" Ames exploded. "The idea sounds crazy!"
"I don't think it'stoocrazy ortoorisky," Tom argued. By emphasizing the words, he hoped to impress them on Ames's mind.
stalling
Tom's tone of voice and the farfetched nature of what he was saying had already triggered the security chief's suspicions. "Where are you calling from?" Ames asked after a tense pause.
"Shopton," Tom replied. "I just drove in for a haircut." With a chuckle, he added, "Haven't had one inthreemonths. That's a wholeweeklonger than I usually go!"
Would Ames understand that by "week" he meantsevendays?... "It's the best I can do," Tom thought.
"Look, skipper, are you sure you want Mirov let out?" Ames said slowly. "I still think it's unwise."
"Consider it an order!" Tom snapped. "This isonething I insist upon, Harlan. Shouldn't take more thanfiveorsixhours, should it, even if he has to wire the Brungarian Embassy to put up bail?"
"It can probably be handled faster than that—if he has any friends around town," Ames said.
Tom took the cue. "Could be," he replied meaningfully.
Tom's captor snatched the phone away and slammed it back on the hook. "All right, smart boy! That's enough!" he growled, glaring at Tom.
Back at Enterprises, Ames hung up thoughtfully. Tom's reply to his last question about Mirov having "friends around town" had convinced Ames that the young inventor was a prisoner, speaking under duress. Moreover, it had seemed as if someone else's breathing was faintly audible in the background, close to the phone.
But what message had Tom tried to convey?
As a routine security-department precaution, Ames's phone was connected to a recorder which automatically taped all calls. Now, while he pondered the problem, Ames pressed a foot-treadle switch to play back the conversation.
Meanwhile, Tom and his captor waited tensely. From time to time the latter glanced at his watch. "Better hope that call does the trick, Swift," he muttered. "It's the only hope you got of leavin' here alive!"
"How will you know if they've turned Mirov loose?" Tom asked. He was wondering if he might persuade his captor to let him make a second call.
"Don't worry. Mirov knows how to contact me."
Half an hour dragged by—then forty minutes. Suddenly the door buzzer rang sharply. The man jerked to attention, obviously startled. He glanced at Tom, then toward the direction of the sound, moistening his lips nervously.
"He must have been expecting just a phone call," Tom decided.
The buzzer shrilled again. This time the man got up from his chair, gagged Tom hastily with a handkerchief, and went to the door.
"Who's there?" he asked loudly.
"Mirov! Let me in, Duffy!" replied an accented voice from outside.
With a look of relief, Duffy started to open the door—then froze as he saw not only Mirov, but two police officers and Ames accompanying him.
"Are you the one who's going to put up bail?" one of the officers demanded.
Duffy floundered, scenting danger but unable to pick up any clue from Mirov's face. "Why—uh—yeah, maybe. How much is it?"
"Ten million! Can you raise it?" Ames snapped sarcastically.
As Duffy gaped in confusion, the officers suddenly flung their weight forward. The door flew open and Duffy was thrown back, almost losing his balance. Beyond, through the small vestibule, Ames caught a glimpse of Tom on the sofa.
"There he is!" Ames shouted.
Moments later, Tom was untied. Mirov and Duffy were handcuffed together.
The young inventor shook hands joyfully with his rescuers. "Nice going, Harlan! Boy, I was sweating icicles here, wondering if you'd be able to decipher all my double talk!"
"You made the numbers clear enough," the security chief said with a grin, "but it took a while to guess what they stood for. And then, of course, we had to trace the address through the telephone company."
Eying the ugly bruise on Tom's forehead, Ames added, "Sure you're all right?"
"Right now I feel swell!" Tom declared, chuckling. He told of his kidnaping, while one of the officers took down the details.
The prisoners were taken off to jail in the police squad car. Tom and Ames, meanwhile, in the security chief's high-powered sedan, drove to the scene of Tom's capture.
They found his sports car badly damaged. The right side was wedged against the utility pole, which was leaning at a crazy angle.
Ames whistled and shook his head. "Boy! You're lucky you got off with just a bruise, Tom!"
"You're telling me," the young inventor agreed ruefully.
After calling a repair garage to send out a wrecker, they drove to the Swifts' home. Mrs. Swift and Sandy, previously unaware of Tom's plight, were horrified to hear what had happened. The sight of Tom's bruise also upset them.
Tom did his best to allay their concern, but finally allowed himself to be hustled up to bed. Dr. Emerson, the Swifts' family physician, was immediately summoned to the house. He pronounced the bruise not serious, but advised that Tom remain quiet, at least for the rest of the day.
Bud came to visit the young inventor that evening, just as Sandy was bringing up a tray. On it was a sizzling T-bone steak.
"Wow! Wish I could have that kind of service," Bud said jokingly. Then he became serious. "I'd sure like to meet that creep who snagged you, Tom. What a fiendish trick! You realize you might have been killed?"
"I realize it, all right," Tom said wryly.
The next morning Tom felt no ill effects from his grim adventure and insisted upon driving to Enterprises. He phoned Admiral Walter, whose report was bleak—the searchers had still gleaned no trace of the buried missile.
Refusing to be discouraged by the news, or lack of news, Tom went to his private laboratory and applied himself once again to the problem of building an "invisible" submarine. But again success eluded him.
At last Tom shook his head in disgust. "May as well get that haircut I started out for yesterday," he decided.
Before leaving, Tom phoned Phyl Newton to thank her for the gift of fruit and nuts she had brought over the previous evening after learning of his dangerous experience. They chatted for a while and wound up by making a date for lunch.
Tom drove back to town in the family car and got a haircut. Then he picked up Phyl at her home and took her to the yacht club. Here they lunched on the terrace overlooking the sparkling blue waters of Lake Carlopa.
The young inventor's spirits were high when he finally returned to his laboratory and buckled down to work.
"I'll lick this problem yet," he muttered. "Those enemies of ours are clever, but if they can produce an undetectable sub, there's no reason why I can't do the same."
Deep in thought, Tom idly fingered a microphone on his workbench.
"In fact," the young inventor mused, "why not go them one better? I'll invent a submarine that's not only invisible to sonar, but equipped tosee them!"
CHAPTER XI
SQUARE-DANCE HOAX
Random hunches and circuit diagrams flashed through Tom's brain. "The job will boil down to blotting out sonar waves and piercing the enemy's own 'wave-trap defense,'" the young scientist concluded.
As Tom struggled with the problem, he lost all track of time. A door swung open and high-heeled boots clumped on the floor tiles. Tom looked up and saw the portly, aproned figure of Chow Winkler entering.
"Hi, boss! Can I borrow a radio?" Chow asked. "Kinda like a lil music while I wrassle them pots an' pans in the galley."
"Sure, pardner." Tom pointed toward a portable radio on a shelf nearby.
Chow's leathery face broke into a grin as he picked it up. "One o' them slick lil transistor doodads, eh?"
The cook flicked on the dial knob and the twangy strains of Hawaiian guitar music came throbbing out. A split second later the volume swelled as the same music echoed back to them from the two-room apartment adjoining the lab, where Tom ate and slept when engaged in some round-the-clock experiment.
Chow was startled by the blare. "You got a stereo hookup here, boss?" he inquired.
"Not exactly." Tom explained that the music had merely been picked up by the mike on his workbench, then fed into the adjoining apartment and amplified over a speaker there.
Chow grinned, snapping his fingers to the catchy melody. "Comes out even louder'n it does from the radio!"
"Yes, but the sound quality's not so good," Tom said. "You'd notice the difference with real stereo."
Chow walked out with the portable, crooning contentedly to the music.
Tom frowned, trying to get his train of thought to focus once more on the submarine problem. But for some reason the business with the microphone and the speaker in the next room kept lingering in his mind.
Suddenly Tom exclaimed aloud, "Say! I wonder if that's how the enemy sub blinds our sonar?"
The idea certainly seemed feasible. Suppose the submarine used a great many "microphones"—or receiving transducers—to pick up the sonar pulses beamed out by another craft trying to detect it? These impulses could then be passed on and sent out by speakers on the opposite side of the sub, and relayed along on their underwater path of travel.
Thus the sonar waves would appear to be striking no obstacle—and no echo would return to the sonarscopes on the search craft!
"Jumping jets!" Tom thumped his fist on the workbench in his excitement. "I'll bet that's the answer, all right!" He grinned. "Brand my boot heels, it's partly due to good old Chow!"
He grabbed a pencil and began sketching his idea on paper. It would be necessary to spot the receivers and transmitters all over the hull of the submarine. Diagrams and pages of scribbled computations followed the rough sketches.
An invisible sub—one that sonar pulses would seem to pass right through, as if nothing were there! "Seems so simple now that I have the key!" Tom said to himself elatedly.
Hours ticked by while he analyzed the wave action mathematically, then worked out a typical hookup for one of his jetmarines in a set of precise schematic drawings.
Finally the young inventor dropped his pencil, picked up the telephone, and dialed Bud Barclay.
"Hop over here, fly boy," Tom told his chum. "Something hot on the griddle!"
Bud arrived in a few moments. Tom showed him the drawings and explained his plan for dodging underwater detection. He also related how Chow's remarks about the radio music had sparked the idea.
His chum slapped him on the back. "Good going, Tom!"
"Let's fly right over to Fearing and see how it works on a jetmarine!" Tom proposed enthusiastically.
Bud grinned but made no move. He stood looking at Tom, arms folded and feet wide apart.
"Well, let's go, pal!" Tom urged impatiently, puzzled by Bud's lack of response.
"What about the square dance?"
Tom stopped short, feeling like a punctured balloon. He stared in dismay at his smiling, dark-haired copilot. "Good night! I forgot again!"
With a sigh, Tom added, "You're right, of course. We sure can't let the girls down twice. But at least let's get together all the gear we'll need when wedogo to Fearing."
"I guess we'll have time forthat," Bud conceded with a sympathetic grin.
Tom assembled a mass of electronic equipment and phoned various Enterprises' departments for other items. Bud helped to collect them, and the boys trucked the paraphernalia out to a hangar to be loaded aboard a Whirling Duck. Then they scootered back to the lab for a quick shower and change.
Twenty minutes later, in sport jackets, checked shirts, and slacks, the two chums hopped into Bud's red convertible. They picked up Sandy and Phyl and drove a little way into the country for dinner at a huge old farmhouse restaurant.
"Well, the evening's off to a good start," Sandy said with a happy laugh as they headed back along the lakeshore road to the yacht club.
"Hope I didn't put away too much fried chicken to sashay properly at the square dance," Bud remarked.
Tom chuckled. "Don't worry, pal. You always untangle those feet of yours when the fiddle strikes up!"
The blazing lights of the yacht club were reflected in the blue-black mirror of the boat basin. Bud parked and they went inside.
"Welcome, buckaroos!" Chow Winkler greeted them with an enthusiastic bellow as they entered the dance room.
The old cowpoke was splendidly dressed in a maroon satin shirt and white whipcord breeches tucked into shiny new boots. But instead of his usual sombrero, a chef's cap was perched on his head.
"Chow! You look marvelous!" Sandy said.
The cook blushed with pleasure. "You gals look purty enough to charm a hoot owl right off'n his perch!" he shot back. Both Phyl and Sandy were wearing gay calico dresses that had full swirling skirts.
The room was decked out with colored bunting and twisted crepe-paper streamers. And at one end of the dance room, Chow had rigged up a model of a Western chuck wagon.
"Real atmosphere!" Tom said admiringly. "Chow, you've done us proud!"
"Thanks, boss." The cook, who had asked especially to take charge of the decorations, glowed at the praise. Then he became serious. "But what's keepin' that dad-blamed fiddler?"
The guests soon began to stream in, but half an hour went by, and Lester Morris and his fellow musicians had not arrived.
"I'd better phone his house," Tom decided worriedly.
Mrs. Morris answered. She seemed surprised at Tom's call. "Why, my husband's playing at a party over in Carterton this evening," she said. "Are you sure you engaged him for tonight?"
"I'm positive," Tom replied.
"Just a moment, please. I'll look in his date book to see if there's been a mistake."
A minute later her voice came over the line again. "I'm terribly sorry, Mr. Swift, but your name isn't listed anywhere on Lester's schedule."
The others saw from Tom's face as he hung up that something was wrong.
"What gives?" Bud asked anxiously.
"No music for one thing." Tom reported what Mrs. Morris had told him.
"But you hired the guy!" Bud protested. "And Sandy and I talked to his agent!"
Tom was already piecing together the mystery. He shook his head thoughtfully. "I'm sure now the whole deal was a hoax, Bud," he declared. "Both the first call that supposedly came from Lester Morris, and the second one asking me to come here and talk things over."
By not responding to the second call in person, Tom went on, he had probably saved himself from being waylaid or kidnaped by his enemies.
"Thank goodness!" Sandy exclaimed. "Still, that creepy Len Unger was trying to get information from us."
"But how did your enemy know about the dance, Tom?" Phyl Newton put in.
Sandy snapped her fingers. "I know! I'll bet it was when we went shopping for our dresses, Phyl, right after the boys invited us! The department store was full of people—almost anyone might have heard us discussing the dance!"
"Especially if he was already trailing you to pick up bits of useful information," Tom agreed.
Bud whipped out a handkerchief and mopped his face nervously. "The question is what do we do now, chums? A roomful of guests and no music!"
"Relax, pardners!" Chow broke in cheerfully. "Just keep things goin' for a spell, an' I'll fix things up pronto!"
Doffing his chef's cap, Chow hustled out to his parked jeep and took off with a roar. Mystified but hopeful, Tom, Bud, and Phyl did their best to entertain the guests. Sandy had rushed to the telephone. In twenty minutes Chow came rushing back.
"Hey! He has a fiddle!" Bud exclaimed.
Mounting the platform, the stout cowpoke raised his hands and shouted for attention.
"Ladies an' gents, we'll start off with that good old dance known as the Texas Star!"
As everyone took his place, Chow tuned up hastily. Then he tucked the fiddle under his chin, stomped out the rhythm, and launched into a lively rendition of "Turkey in the Straw" while he called out the accompaniment:
"Gals to the middle, then back so far!Gents step up for a clockwise star!Now shift hands and twirl t'other way,We'll keep on dancin' till the break o' day...."
The dance number finally ended to thunderous applause. Chow, puffing and red-faced but wreathed in smiles, was soon ready for another. Half an hour later, a dance band of high school boys, hastily summoned by Sandy, arrived to spell the Texan.
The irrepressible chef, however, continued to call out most of the numbers and proved to be the hero of the evening. He gained even more acclaim for his delicious French fried potatoes and "steerburgers" served during the pause for refreshments.
"Oh, Chow! What would we ever do without you?" Sandy said, and the cook beamed.
Suddenly, in the midst of the lively chatter and laughter, the dance floor was plunged into total darkness!
Phyl clung fearfully to her escort. "Tom!" she gasped. "This is another trick of your enemy's to harm you!"
CHAPTER XII
DETECTION TEST
"Don't worry, Phyl. It may be only a blown fuse," Tom tried to assure the fearful girl.
But Tom was worried himself. Not only might he be in danger, but it could involve his friends!
Nevertheless, he raised his voice above the excited babble. "Please be calm, everyone! We'll have the lights on again in a jiffy!"
Taking Phyl by the hand, Tom groped his way toward the main door.
"Let's check the switch," he murmured, and ran his hand over the wall near the door. He located the metal plate and flipped the switch.
The lights went on! Good-natured cheers arose. Bud, grinning but puzzled, left Sandy's side long enough to come over and speak to Tom.
"What happened?"
"I guess some practical joker clicked off the switch."
Bud suddenly caught sight of a stout youth in a plaid shirt and blue jeans, who was standing in a nearby corner. He was shaking all over with half-stifled merriment.
"There's the wise guy! Rock Harriman!"
Rock, an all-star tackle on the Shopton High football team, was well known for his pranks and practical jokes. Bud rushed over.
"Okay! Confess!" the husky young flier roared in a jokingly ferocious tone.
"Don't get sore!" Rock gasped between chuckles. "I couldn't resist. Boy, did you hear everyone squeal when the lights went out?"
Tom grinned in relief. "How about another dance, Phyl?"
As the music struck up again, he squeezed Phyl's hand. "I sure appreciate your concern, even if I didn't rate it."
Phyl blushed as she returned the squeeze. "You rate with me," she confided shyly.
The festivities finally ended after a thoroughly enjoyable evening. Both Sandy and Phyl declared to their dates that it more than made up for the forgotten beach party.
"But let's not wait too long for the next date," Sandy warned playfully.
"Okay, that's a deal," Bud promised.
The next morning at the plant Tom called on Harlan Ames. He told of the sinister hoax by the caller who had passed himself off as Lester Morris. The security chief promised to investigate.
"I'll tip off the police about Len Unger," Ames added. "If they can find him, we may be able to crack this case wide open."
Tom telephoned Bud, Hank Sterling, and Arv Hanson to meet him at the helijet hangar. The four took off in one of the Swifts' Whirling Ducks, which was standing by loaded and ready. Soon they landed on Fearing Island, where Tom would try out his antidetection invention.
"What'll we use for a test sub, skipper?" Hank asked as they drove toward the docks.
"A jetmarine," Tom replied.
A truck with engineers and technicians was following the jeep. It carried the equipment which Tom and Bud had assembled the previous day.
When they arrived at the docks, Tom gathered the men in a loading shed. He showed them his drawings and explained how his "sonar-blinding" setup would operate.
"Don't let the diagrams fool you. The basic idea is very simple. We absorb all sonar impulses that hit the ship and transmit them out the opposite side of the hull, instead of letting a ping bounce back and show up on the sonarscope of any hostile sub on the lookout for us."
Most of the job, he went on, would be tedious detail work. It would consist of attaching hundreds of mikes and speakers all over the hull to pick up and transmit the sonar pulses. The mikes would be receiving transducers and the speakers would be transmitting transducers.
"The leads from them," Tom ended, "will be centralized in a single electronic control unit inside the ship. I'll handle that part of it."
"Great idea, Tom!" Arv Hanson said admiringly.
"But what a job it'll be rigging those transducers," put in one of the technicians.
Tom nodded wryly. "You're right, Danny. If this experiment works out, though, I think I can lick that problem on future installations."
The young inventor explained that he hoped to find a way to mold the transducers into a continuous plastic sheet. This could be applied to the hull of a submarine in a single operation.
"But this time we'll have to do it the hard way," Tom added with an apologetic grin.
A jetmarine was hoisted into drydock and the work crew swarmed over it, rigging the transducers. Would his experiment succeed? Tom wondered. Hopefully, he set to work assembling the electronic control unit.
Bud helped the men on the hull for a while, then descended through the hatch to see how Tom was progressing.
experiment
"I'd go gaga trying to keep track of those circuits," Bud said, as he watched Tom installing the delicate transistors and other components with an electric soldering gun.
The young inventor grinned. "It'll be simple enough when the control unit's all put together," he replied. "Just a single on-off switch and one test circuit."
By noon, after working at a frenzied pace, the job was done. Tom thanked each one of the men personally. Then everyone went to eat lunch.
After the meal, Hank Sterling asked, "How about a detection test to see how she works?"
"Coming right up," Tom said. "Want to skipper the jetmarine, Bud?"
"Sure do!"
"Okay. Pick out a couple of men for a crew and take her down." Tom produced a hydrographic chart of the waters around Fearing and marked out a test area. "Cruise around there for an hour and we'll try to spot you in theSea Hound."
"Hide and seek, eh?" Bud grinned and snapped a salute, then left to supervise the relaunching of the jetmarine.
For his crew, Bud chose Mel Flagler and another man. Mel was an experienced jetmariner who had gone on the Swift expedition to Aurum City, the underwater ruins of a lost civilization. Here Tom had used his spectromarine selector to restore the ancient buildings.
Tom, Hank, and Arv went back to the airfield and soon took off in the diving seacopter. Landing on the water, they submerged and began the undersea detection test.
Tom manned the sonarscope personally, eager to conduct as careful a search as possible.
"Getting any blips, skipper?" Hank called out from his post at theSea Hound's controls.
"Not a ping, Hank. The system seems to be working out even better than I'd hoped."
Tom felt a glow of satisfaction. He explained, however, that the jetmarine's transparent nose pane—which had to be left unprotected for the pilot's visibility—offered one vulnerable spot to sonar detection.
"But a little smart maneuvering can cover up that angle," Tom added. "Try the hydrophones, Arv, and see if you can hear 'em."
The chief modelmaker slipped on the earphones and listened intently. For another ten or fifteen minutes they probed about with no sound trace of the "invisible" jetmarine.
But presently Arv snapped his fingers to catch Tom's attention. "Got her, skipper!"
Tom took over the hydrophones. Sure enough, his ears could make out the faint hum of the jetmarine's atomic turbines. Tom directed Hank toward the sound, then ordered him to switch on theSea Hound's powerful search beam.
The light cut a path of radiance through the murky dark-green waters. Dead ahead, the jetmarine could be seen gliding across their field of view.
"Your system blinded our sonar okay, skipper," Hank commented, "but this proves she could still be spotted by enemy listening devices."
Tom refused to be discouraged. He ordered Hank to return to base and wait for Bud. Meanwhile, the young inventor applied himself to the problem of how to mask the sub's noise.
"How about it, pal?" Bud asked, when he reported aboard the seacopter a while later.
Tom explained the results of the test and the need for an added safeguard against hydrophone detection. "Think I see a simple way out, though," he added with a pleased chuckle.
"Natch! With a brain like yours, it's a cinch," Bud quipped. "Explain, professor."
"Well, we can never do away with the noise of a sub's propulsion machinery," Tom began. "That goes without saying. So we'll have to camouflage it—lose it in the underwater jungle noises, so to speak."
Bud scratched his head. "How do we do that?"
"By amplifying the natural undersea sounds all about it," Tom explained. "Fish and all forms of underwater life make a background noise over the hydrophones, you know."
As Bud nodded, Tom went on, "So we simply step up the volume till the sub's own noise gets drowned out or 'wasted' in all the racket."
This could be done, he concluded, with fairly simple amplifying equipment. Bud, Hank, and Arv were jubilant at the idea.
"Nice going," Bud said. "How soon can we give it a try?"
"Soon as I can rig up the amplifier," Tom promised.
In less than two hours they were ready to submerge again. Zimby Cox joined the crew. Bud suggested taking along hydrolungs in case of any need for tinkering with the transducers or amplifying equipment.
This time, the jetmarine scored perfectly on the test, successfully eluding all theSea Hound's efforts to detect it. Tom returned happily to base, feeling that the antidetection problem was now solved. The jetmarine, however, failed to appear.
"That's funny. The test was over at four-fifteen," Tom murmured.
"Maybe Bud surfaced out at sea somewhere," Arv Hanson suggested.
Repeated radio calls brought no response. Tom, now seriously worried, took the seacopter down again for another search, hoping that Bud would have switched off the antidetection gear by this time. But neither sonarscope nor listening devices revealed the slightest clue.
Tom, Hank, and Arv exchanged fearful glances. Had the jetmarine foundered on the ocean bottom—perhaps fouled somehow by Tom's new invention? Or had Bud and his crew fallen victim to the enemy?
CHAPTER XIII
ENEMY FROGMEN
At the end of the test period, Bud had prepared to bring the jetmarine to the surface. But just as he was about to blow the ballast tanks, Mel Flagler sang out a warning from the sonarscope.
"Whoa! Hold it, skipper! I think we have company on the starboard beam!"
Bud jerked his head around in surprise. "You mean theSea Hound?"
"No, she surfaced," Mel reported. "Can't make this out yet, but it could be another sub."
Bud turned the controls over to Zimby Cox. Then he rushed to the scope and examined the blip. "Seems to be moving away from us on a westerly course. It's about two miles from here."
He donned the hydrophone earset and listened. "It's no seacopter, nor a jetmarine either," he announced presently.
"A Navy sub, maybe?" suggested Zimby.
Bud shrugged. "Let's find out." He ordered a change of course, hard to the right, and gunned the jets to bring the jetmarine directly on the mystery object's trail.
"It's a sub, all right," he said a short time later, listening again over the hydrophones.
"Pretty close to Fearing Island, isn't it?" put in Mel Flagler. "That's a government-restricted area."
Bud nodded grimly. "But staying just out of sonar range from the base."
The jetmarine closed steadily on its quarry. In a few minutes they were able to make it out dimly through the cabin window, dead ahead.
"That's sure no U.S. Navy sub that I know of," Bud said. "Probably an enemy snooper."
"What if they spot us?" Zimby asked.
Bud chuckled. "That's the beauty of it, pal! Don't forget. With this new antidetection gear we're invisible to them. At least as long as they don't run into us or we into them," he added.
"Or unless they have superdetection equipment we don't know about," cautioned Mel Flagler.
As they talked, the unidentified submarine was bearing steadily toward the mainland. Fathometer soundings showed it was on a steep upward slope of the continental shelf.
Presently a foaming gush of bubbles showed that the sub ahead was blowing its tanks. The jetmarine followed as it surfaced and Bud hastily manned the periscope.
"What're they up to?" Mel asked tensely.
"Don't know yet, but the hatch is opening," Bud reported. Suddenly he gave an excited gasp. "Jumpin' jets! They're sending out a couple of frogmen!"
Bud's companions were electrified by the news.
"Spies!" Zimby exclaimed.
"What do we do now?" piped up Mack Avery, the third man in Bud's crew. "Hadn't we better radio the Coast Guard and the FBI?"
Bud wrenched away from the eyepiece. "I have another idea! Any of you fellows game to go with me and capture those spies?"
All three of his companions volunteered eagerly. Bud chose Mel Flagler, then took another sight through the periscope.
"The sub's submerging again," he reported. "That'll give us a clear field. Zimby, you and Mack keep an eye on that baby while we're gone, and be plenty careful she doesn't spot you!"
"Roger! And take this roll of wire to tie up your prisoners."
Hastily Bud and Mel changed into swimming trunks and donned hydrolungs. They went out through the air lock, plunged into the bracing salt water, and switched on their ion-drive units.
"Can you see 'em?" Mel asked over his mike.
"Not yet. Let's speed up before we lose 'em completely!"
Both pushed their ion drives to capacity, scanning the water ahead in all directions.
"There they are!" Bud exclaimed presently. He pointed to two tiny figures, barely visible in the distance.
"Wow! They're sure not wasting any time!" Mel muttered. "Let's step on it, Bud! They'll be ashore in a minute!"
A darting school of sea bass screened the figures briefly from view. As the fish flickered past, Mel and Bud saw the frogmen breast-stroke up toward the surface and break water.
Bud and Mel followed. Ahead lay a barren stretch of beach, humped with sand dunes. It was skirted beyond by a thick fringe of trees.
"They certainly picked a perfect spot for a sneak landing!" Bud thought. The beach seemed totally deserted, with no sign of human habitation.
By this time, the frogmen were scrambling ashore. Within moments, Bud and Mel were on their heels. The raiders whirled in dismay as they caught the sound of footsteps rushing up behind them through the sand.
Bud and Mel hurled themselves forward, each dropping a man with a flying tackle. All four went down in a struggling, kicking tangle of arms and legs.
The battle was rough but short. Bud and Mel had the advantage of surprise, and soon pommeled and grappled their foes into submission.
Bud, astride his opponent's chest with knees pinning the man's arms, unlooped from his belt the wire he had brought.
"Here! Take some of this and wire your man's wrists together!" Bud told Mel.
When the frogmen were safely bound, Bud and Mel allowed them to stand up. Neither captive tried to escape.
"Now, my sneaky friends, talk!" Bud snapped. "What kind of a sightseeing trip did you plan?"
The frogmen's jaws remained tightly clamped. Both looked flushed and sullen as they faced their captors.
"Got their lips zipped, I guess," Mel said disgustedly.
Bud decided to try another tack. "Doesn't matter," he said carelessly. "We know they're pals of the Mirovs."
Both men started as if they had been stung. Bud followed up quickly, hoping to prod them into some unguarded remark.