TOM

SWIFT AND HIS DYNA-4 CAPSULE

BY

VICTOR APPLETON II

Tom Swift Jr. - 31

From the front: What are the green glowing bubble creatures that the young scientist-inventor encounters in the depths of the Pacific Ocean? How do they rescue Tom and his pal Bud Barclay from an attack by the fish men?

Tom's electrifying adventures begin deep in the Mariana Trench where he has based his newest invention, the Dyna-4 Capsule, in a hunt for rare metals. A super submarine, the craft has been especially designed for deep-sea research and exploration.

On orders from Washington, Tom takes time out from his own project to recover a stolen vial containing a highly destructive explosive. The top-secret mission turns into a danger-filled whale chase in the Dyna-4 and leads to a showdown with Tom's ruthless foes.

ILLUSTRATED BY RAY JOHNSON

GROSSET AND DUNLAP

COPYRIGHT © 1969 BY GROSSET & DUNLAP, INC.

ALL RIGHTS RESERVED

PUBLISHED SIMULTANEOUSLY IN CANADA

LIBRARY OF CONGRESS CATALOG NUMBER: 69-12165

PRINTED IN THE UNITED STATES OF AMERICA

The Tom Swift Jr. Series:

1 Tom Swift and his Flying Lab (1954)

2 Tom Swift and his Jetmarine (1954)

3 Tom Swift and his Rocket Ship (1954)

4 Tom Swift and his Giant Robot (1954)

5 Tom Swift and his Atomic Earth Blaster (1954)

6 Tom Swift and his Outpost in Space (1955)

7 Tom Swift and his Diving Seacopter (1956)

8 Tom Swift in the Caves of Nuclear Fire (1956)

9 Tom Swift on the Phantom Satellite (1956)

10 Tom Swift and his Ultrasonic Cycloplane (1957)

11 Tom Swift and his Deep-Sea Hydrodome (1958)

12 Tom Swift in the Race to the Moon (1958)

13 Tom Swift and his Space Solartron (1958)

14 Tom Swift and his Electronic Retroscope (1959)

15 Tom Swift and his Spectromarine Selector (1960)

16 Tom Swift and the Cosmic Astronauts (1960)

17 Tom Swift and the Visitor from Planet X (1961)

18 Tom Swift and the Electronic Hydrolung (1961)

19 Tom Swift and his Triphibian Atomicar (1962)

20 Tom Swift and his Megascope Space Prober (1962)

21 Tom Swift and the Asteroid Pirates (1963)

22 Tom Swift and his Repelatron Skyway (1963)

23 Tom Swift and his Aquatomic Tracker (1964)

24 Tom Swift and his 3D Telejector (1964)

25 Tom Swift and his Polar-Ray Dynasphere (1965)

26 Tom Swift and his Sonic Boom Trap (1965)

27 Tom Swift and his Subocean Geotron (1966)

28 Tom Swift and the Mystery Comet (1966)

29 Tom Swift and the Captive Planetoid (1967)

30 Tom Swift and his G-Force Inverter (1968)

31 Tom Swift and his Dyna-4 Capsule (1969)

32 Tom Swift and his Cosmotron Express (1970)

33 Tom Swift and the Galaxy Ghosts (1971)

CHAPTER I

HARPOON DANGER

"SKIPPER!" Bud called excitedly from the sonar room of Tom Swift's diving copter the Sea Hound "You have a message from a U. S. Navy sub - and it's urgent!

Eighteen-year-old Tom and his pal Bud Barclay had taken the Sea Hound into the deep Pacific. With them were Swift Enterprises' faithful cook Chow, Hank Sterling, and Arv Hanson. They were on their way in the sea-and-air craft to find a suitable location for Tom's new underwater research project.

Tom hurried to the audio receiver and listened intently to the submarine commander's startling message.

"This is Harper. Tom, an unbreakable vial containing a new and top-secret explosive has just been stolen from a team of American research scientists working in the Philippines."

"What!" Tom exclaimed.

"Washington," Harper went on, "wants you to help find it."

The officer explained that there had always been the danger of enemy agents stealing the sample of the explosive.

"The substance has extraordinary destructive capabilities. For this reason," he said, "the small black vial which contains the secret explosive is equipped with a hidden signal unit so it can be traced by radio or sonar."

"Clever idea," Tom said to himself. "That'll make it a lot easier for us to trace."

"The vial," continued the sub commander, "was to be flown from Manila to Washington in a Navy plane. As it was being brought down from the mountain research station by jeep, it was stolen by what were thought to be bandits.

"But they were not ordinary thieves. When the scientists in the jeep described the leader to intelligence authorities in Manila, he was identified as Ignace Sandor, a ruthless enemy agent."

"That figures," Tom said, knowing how actively hostile Brungaria, the man's country, had been to the United States over a period of years.

"We have good reason to believe that the men who stole the vial escaped by sea. The transmitter unit emits signals in the ultrasonic frequency range; they're inaudible to human ears. The unit is concealed in a false bottom on the vial. It is detachable and has a quartzose base for transmitting. The whole thing is painted black, so the chances are the thieves aren't aware that a signal is being sent out. Can we count on you to hunt for the vial?"

"You bet you can, Commander," Tom responded. "We'll do our best."

"Fine, Tom. I'll inform Washington. Before we sign off, I'll give you the pattern of the signals sent out by the transmitter in the base of the vial. Their vibration pattern is unique and easily distinguished from the 'talking' of undersea creatures."

Tom quickly recorded the alternating series of sonic wave pulses. Then he asked how the explosive could be detonated.

"That's a government secret, Tom," the commander replied, "and the Brungarians would need a long time to figure it out. Eventually, of course, they could, but we must get that vial back before they do."

As the Sea Hound proceeded at top speed, Bud said, "How did the Navy know we're out here, Tom?"

His chum grinned. "Washington has been very interested in our Dyna-4 Capsule - and that's why we're here, of course. Guess they've been keeping pretty close tabs on what we've been doing and where we've been."

The Dyna-4 Capsule, Tom Swift Jr.'s latest invention, was an underwater super laboratory, especially designed for investigation in deep-sea environments. It consisted of a central control-and-power unit with four laboratories attached to it. Each was equipped for work in a different branch of science-biology, geology, chemistry, and metallurgy.

"It's a good thing, Tom, that your trip to find a location to anchor the Dyna-4 is over," said Bud.

Tom had picked a spot in the vast and forbidding Mariana Trench, one of the deepest known places in the world's oceans-more than 36,000 feet down.

"The exploratory work we were about to begin in the trench," he said, "will have to wait. First we must rescue that secret vial."

He set the Sea Hound in an automatic spiral search course.

It was not long before Bud exclaimed, "Tom, we're picking up the vial signal on our sonar!"

"You're right. It seems to be coming from the surface. Let's take the Hound up."

Sending the craft quickly to the top, the boys scanned the surrounding ocean.

"There's the source, Bud!" Tom pointed excitedly to an old-time whaling ship lying not far away. "They have the secret vial!"

Warily Tom maneuvered the Sea Hound nearer the vessel. "Whaler ahoy!" He shouted.

To the boys' surprise, voices with foreign accents hailed them from the bridge and invited the Americans aboard.

"They certainly sound friendly," Bud commented, "but let's not take any chances."

"Right, pal," Tom agreed. "Somebody on board that ship has the Navy's stolen vial. And you can bet he'll do everything possible to keep us from finding it.

"We have one advantage, Bud. He probably hasn't found out about the transmitter, so he can't have any idea that we suspect him. Anyway, I'll take my pencil radio to keep track of the signal and my repelatron wrist watch, just in case."

The Sea Hound was close to the whaler now. Tom edged it in cautiously to the side of the huge old ship.

Prospects for a pleasant reception seemed less likely at close range. Tom noted that one of the surly-looking crewmen was poised at a harpoon gun on the forward deck. Presumably the crew was on the alert for whales-but, Tom thought, that harpoon gun could be a lethal weapon if fired at Bud or him!

Leaving Arv Hanson at the controls of the Sea Hound with instructions to follow the whaler if she tried to get away, the boys, accompanied by Hank Sterling and Chow, climbed aboard.

The trio were good friends of Tom and Bud and long-time employees of Swift Enterprises. Arv Hanson, who headed the model-making division, was blond and big-boned; the chief pattern-maker, Hank Sterling, was light-haired and lean. Only Chow Winkler, formerly a Texas ranch cook, suffered from overexposure to his special Western dishes. The size of his waist was a perfect match for his broad, happy-go-lucky smile.

They had just set foot on deck when one of the ship's crew shouted, "Thar she blows!" A huge sperm whale had surfaced off the bow!

Immediately the ship went into action. The captain hove the vessel nearer the whale. Carefully timing his shot, the crewman at the harpoon gun fired the huge shaft into the mammal's back.

The sea became a seething froth as the creature dived to escape the enemy who had wounded it. The line from the harpoon unraveled at a fierce pace to its full length - and broke! The whale escaped, taking the harpoon with it!

"Tough luck," Bud remarked. "That old fellow must have gone crazy when he was hit. Ordinarily sperm whales don't move that fast."

Tom whispered to his pal, "The signal from the vial just stopped!"

During the exciting action, Tom had been listening carefully to the signals from his pencil radio. Now they were gone!

The boys' attention was diverted by the whaler's captain, who was corning down from the bridge in a towering rage, shouting and swearing.

"This guy sure is a poor loser," Bud said. "Listen to him over the loss of one whale."

"I wonder," mused Tom. "Could. . .?"

"Wonder what, skipper?" Bud asked quickly.

"Look over there," Tom said in reply, pointing to a thin-faced, dark-haired man. "That's Ignace Sandor, the Brungarian agent! I recognize him from the Navy's description and a picture I saw of him."

Advancing toward the agent, Tom decided on a direct approach.

"All right, Sandor," he said, "I know you, and I know you have the secret vial. Where is it?"

Surprised only for an instant, the agent swiftly whipped out a small hand weapon and pointed it at the visitors.

"Watch out!" Tom warned his party. "That's a ray gun!"

Sandor fired point-blank at Tom, but the young inventor deftly deflected the beam with his repelatron wrist unit.

The exchange between Tom and Sandor had alerted the whaling crew. The hostile and menacing men surrounded the young inventor and his party.

"Looks as if we're in for trouble," whispered Tom. "Let's try to fight our way over the side and back to the Sea Hound."

But the crew closed in. A muscular sailor in a striped shirt lunged at Tom with a harpoon. Dodging and feinting, Tom warded off the harpoon's thrust and yanked the shaft hard, bringing his right fist up into the man's solar plexus. The air went out of his lungs with a whoosh, and he collapsed gasping on the deck.

Beside him, Tom could see Bud and Hank Sterling giving a good account of themselves. Chow had two crew members by their heads and was knocking them fiercely together.

Just then a light exploded in Tom's head and he felt himself falling forward. Dazedly he rolled onto his back. Poised over him, a knife upraised to strike, was Sandor, his eyes cold as ice.

As Tom struggled to clear his head, Chow's familiar face suddenly appeared behind the Brun-garian agent. Grabbing Sander's knife arm, Chow hurled him backward with tremendous force against the railing.

"Good work, Chow," said Tom, getting to his feet. "You saved my life! Come on. Let's go over the side while we have a chance." He motioned to Bud and Hank.

The four quickly slipped over the ship's rail and into the Sea Hound, which Arv Hanson had kept alongside. As Tom closed the hatch, he heard the whaler's captain calling for depth charges.

"Arv, take her down-fast!" Tom shouted. "We're going to be depth-bombed!"

The Hound streaked rapidly for the safety of the deep ocean - but not rapidly enough. Tom and his friends heard a tremendous whoom as the first charge exploded nearby. Then he was thrown against the bulkhead. Everything went black!

CHAPTER II

A RUINED REACTOR

IT was some time before Tom regained consciousness. He sat up on the cabin floor and looked around him, his head throbbing.

"What about the others?" Tom thought. "Bud!" He called, struggling to his feet.

A moan from across the cabin brought the young inventor to his chum's side.

"I'm okay, Tom - I guess." Bud groaned. "Just shaken up. How bad is the damage?"

"I'm not sure yet," Tom answered.

The place was a shambles. Everything loose or movable had been tossed around. The scene was illuminated only by the dim light from the battery-powered emergency lights-which meant that the main power was off.

"We must be resting on the bottom," Tom said. "There's apparently no damage to the Sea Hound itself, but you can see for yourself the main power is off. Come on. Let's find out if anybody is injured."

A quick check of the crew revealed that they had been extremely lucky. Aside from a few assorted cuts and sprains, there were no major injuries.

The seacopter might be another story. Without power it could not move.

"We'd better hunt for the source of the trouble," Tom urged.

Bud said, "I wonder what happened to the whale."

"Probably got tossed around, but is probably okay. I'm more worried about us."

After an hour spent poring over blueprints and examining the complex wiring and plumbing of the Sea Hound's, atomic power system, Tom exclaimed, "Here's our trouble, Bud! This is why we're sitting here with no juice."

He pointed to an intricate section of the piping and valves on the side of the reactor nearest the outer shell of the craft.

"Those feedback valves have been buckled by the shock wave of the depth charge. My guess is that the jam-up raised pressure to the danger point, which automatically caused the system to shut down."

"What are our chances of releasing the pressure, skipper?" Bud asked anxiously.

"Not too good, I'm afraid," Tom replied ruefully. "In fact, it looks just about impossible, I'd say, unless we can dismantle that whole section of the ship-which we can't."

Hank and Arv, who had entered the power room while Tom was talking, looked bleak at the prospect.

"Tom, there must be something we can do," said Bud.

"I have an idea," the young inventor told him. "I think it'll work, but we must check a few things first."

He bent over the vessel's wiring diagrams and began making quick calculations. Finally Tom straightened up with a sigh of relief.

"This ought to get us out of the spot we're in," he said. "I wasn't too sure at first, so I wanted to check the wiring.

"Instead of trying to unjam these valves, we're going to by-pass them. Our navigational computer is okay. We'll just rewire the reactor controls so the navigational computer turns it on and off. We'll be taking a chance, of course, because there won't be any automatic safety shut-off. But we should be able to make port this way."

"I knew we could count on genius boy here," Bud said gleefully. "Well, let's get to work."

With power restored, another problem became evident: the communications computer had been damaged.

"But at least we can move," Hank spoke up.

As the Sea Hound limped toward Manila, the nearest large port, Tom discussed their encounter with the whaler.

"You know, Bud, the more I think about it, the more I'm convinced that the vial we're looking for was attached to the harpoon head that was shot into the whale."

Bud nodded. "You mean that's the reason the signal quit just as the critter escaped?"

"I don't think it quit. My pencil radio wasn't functioning. Needs a new battery, I guess. Bud, I believe the captain figured that the whale was the safest place to hide the vial, and he'd retrieve it after we'd gone. No wonder he was mad when that harpoon line broke!"

Bud chuckled. "He outsmarted himself."

"One thing that made me suspicious of those men," Tom went on, "was their old ship and its outdated equipment. Modern whale hunters use an exploding harpoon head which kills the whale. I doubt that this old tub is used for whaling any more."

Bud nodded in agreement. "The ship flew a neutral flag, but I'll bet the crew was in the pay of the Brungarians."

"Yes," said Tom. "They must have thought that pretending to hunt whales would be a good cover for escaping with the vial."

The sun was halfway down the afternoon sky when the Sea Hound finally made its entry into  Manila Bay. Tom, Bud, Arv, and Hank made a careful examination of the crippled craft. Then, leaving Chow on guard, they hurried off to buy the needed replacement parts. The brief tropical dusk had already fallen by the time they returned.

"Where's Chow?" Queried Bud as they came down the dock.

Tom frowned. "I'm afraid something has happened to him!" He exclaimed.

The two boys raced below deck. Chow was gone, and the communications computer had been damaged still further.

"Who could have done this?" Bud moaned, viewing the wreckage in the craft's computer room.

"My guess is that the whaler radioed the Brun-garian government about its encounter with us. They probably have a network of agents combing the Pacific for us just in case we escaped the depth charges," Tom said, trying to conceal his anxiety. "But the shambles here is the least of it. What's happened to Chow?"

"Tom!" Hank Sterling called from the dock. "There's a boy out here who says he knows something."

Tom ran up to the dock. Hank and Arv Hanson were talking to a scrawny child of nine or ten. As Tom approached them, the boy burst out, "You look for fat man. Was here before."

"Fat man," Tom said to himself. "Chow would love that." Aloud, he replied, "Yes. You have seen him?"

"Yes, mister. Man come up to him. They go to buy souvenir." He pointed to a curio shop on the road behind the dock.

"Arv, you and Hank stay here with the Sea Hound," said Tom. "And you'd better watch out! Our enemies might be back. Bud and I will look for Chow."

The boys hurried along the dock.

"Now what?" Bud asked when they reached the curio shop and found it closed.

"Let's take a look down that alley in back," Tom suggested.

Daylight was all but gone by now, and the alley was almost completely dark. The boys walked along it cautiously. A dull groan stopped them short.

"Sounds as if it came from over there!" Tom exclaimed, indicating a huge basket outside the rear door of the curio shop.

Tom's suspicions were well founded. Inside the basket was Chow's bulky form, tied hand and foot and he was gagged. The boys quickly released him.

"Chow! Are we glad to see you! What happened?" Tom asked.

Rubbing his wrists, although he was more humiliated than hurt, Chow said sheepishly: "Wai, fellas, this hombre came up to me on the dock with a great-lookin' piece o' glass art. He was offerin' to sell it fer next to nothin', so I bought it. Anyhow, he said he knew where I could get lots more, just as cheap-meanin' this shop here.

"Since it was so close to the dock, I figgered I could make a fast trip an' still keep an eye on the Sea Hound. The dirty rapscallion led me down this alley, an' the next thing I knew - whammo! Reckon somebody bopped me on the head. I woke up in the basket."

"The important thing is that you're okay," Tom put in. "By the way, Chow buddy, where is this fantastic piece of glasswork you're talking about?"

"Oh, it was right here in the basket with me," he said, smiling. "Sure is the most mar-veel-ious thing."

Reaching down, he pulled out what Tom immediately recognized as the root part of a glass sponge - a delicate and artistic structure, but completely natural and quite common-often sold fraudulently as a work of art.

When Chow realized that he had been gypped, his face turned red with anger. "Why, that con-sarned crook!"

Bud grinned. "Chow, you know that mar-veel-ious thing will look absolutely great in the galley." Chow withered his tormentor with a dark look.

"Come on!" Tom urged. "We have work to do. Those men weren't just small-time crooks. That computer has to be fixed at once."

"You mean they busted it up some more while I was in that basket?" Chow gulped.

"I'm afraid so," Tom told him.

It was a thoroughly repentant cook who bumbled along sheepishly back to the seacopter. The tropical night had blanketed Manila by now. Soon the group sat down to eat a long-delayed supper-prepared with extra care by Chow, anxious to atone for his mistakes.

Right after supper Tom and Bud, with the assistance of Arv and Hank, set to work on the damaged computer.

Though the four knew the inner workings of the Sea Hound down to its last rivet and terminal board, it soon became evident that restoring power and communications to the craft was going to be no easy task. Dawn was breaking when they finally finished.

"Boy, that was one tough job!" Bud remarked wearily as he put away the last of the tools. "Shall we get some rest?"

"I know we're all tired," said Tom, "but I think we ought to get under way. We can set the Hound on autopilot and it'll track the vial automatically. Then we can take turns getting some sleep. What do you say?"

"Okay by me." Bud yawned, and the others agreed.

The shrill jangle of an automatic warning bell in the sonar room woke Tom. The view screen showed some large object trailing them! Tom hurried anxiously to the underwater scope.

"Look at the length of that thing!" He exclaimed as Bud came into the cabin.

"What is it? What's happened?" His chum asked.

"We're being tailed by a sub that's the longest one I've ever seen underwater! I don't know whose it is, but I can guess!"

The monstrous craft continued to grow in the scope's view screen!

"Torn," exclaimed Bud, "whoever's running that thing is heading straight for the Hound. It's going to ram us!"

CHAPTER III

TELLTALE MEDALLION

TOM leaped to the controls of the Sea Hound. The craft veered off to the right of the sub's path. Within minutes the smaller craft's power and maneuverability had left the big menace behind.

"Whew, that was close!" Bud gasped.

"It certainly was," Tom agreed. "But I was pretty sure the sub wouldn't be able to change course fast enough to catch us before we got up speed. And I knew we could outrun it, given an even chance.

"That sub is pretty remarkable," Tom continued. "I've never seen anything like it for speed and power underwater-except our faithful Sea Hound of course!"

"Got any ideas about who owns it?" Bud inquired.

Tom nodded. "The CIA tipped me off some time ago when they heard rumors of a new, black super sub. Want to guess who developed it?"

"Would it be the Brungarians, by any chance?" Bud asked.

"You win," Tom replied. "Anyway, I'm sure that's our mystery craft. It all fits in, especially since we know that Brungarians are already after us. They call their sub the Conus, by the way, after the cone shells."

"Hm!" Said Bud. "They're carnivorous and carry a venomous dart."

"Right, pal. Pretty appropriate, don't you think? The Conus carries all manner of deadly weapons systems on board," Tom revealed.

Just then Hank Sterling announced over, the intercom, "Radio message for you, skipper."

"Be right there," Tom responded, turning over the controls to Bud.

When Tom returned a short time later his face was a mixture of emotions. "I guess we can relax a little," he said. "That was the Navy. Seems they've picked up the track of the whale and expect to catch it. They'll tranquilize the beast and regain the lost vial any minute now. So they thanked us for our help and released us from the search. Sure wish we could have been in on the catch, though.

"Well, we still have our own project. Let's get the Sea Hound airborne so we can reach Tokyo as quickly as possible."

The sleek craft was soon streaking through the sky as easily as it had made its way underwater.

Before the afternoon was well advanced, Tom landed the Hound expertly in Tokyo. Here it was stored aboard the. Sky Queen, Tom's Flying Lab, for the long hop back to Shopton.

Even though Shopton lay half the world away from Tokyo, only four hours passed before Tom was bringing the Sky Queen down in the foursquare-mile tract of Swift Enterprises.

After securing the craft and her cargo, Tom hastened to his father's office. Tom Swift Sr. Was studying a sheaf of papers, concern showing on his face.

"Tom!" He cried elatedly. "Glad to see you, son. I've been following your reports from the Pacific. You've done a great job. How was your trip home?"

"Uneventful, Dad," Tom replied. "But you look worried. Anything wrong?"

"I Don't know. There have been a series of recent slow-ups in the work on the Dyna-4 Capsule. They've always been the result of accidents, but frankly I now suspect sabotage."

"Sabotage!" Tom was shocked. "Have you discussed this with Harlan Ames?" He asked.

"Yes, I have," his father replied. "He assures me that our security force investigated each incident in detail but found no evidence to support the sabotage idea. Nevertheless, these accidents are all too convenient. They certainly have slackened the Dyna-4 project to a walk."

"I guess all we can do is be doubly alert," said Tom. "First thing in the morning I'll make a tour of the whole place and see what the status of the operation is."

Immediately after breakfast Tom set out on his checkup tour. He was accompanied by Bud and Chow.

"Let's try the model shop first," Tom suggested, and headed for a sprawling concrete building. "They ought to have the Dyna dummy about finished by now."

"Dyna dummy! What's that?" Asked Chow.

"You'll see. It's an almost full-scale mock-up of the Dyna-4. In fact, it has everything but power," Tom explained as they entered the shop. "I'll keep it as a model in case something happens to the regular Dyna."

He pointed to an oval craft with four winglike projections to which the labs were to be attached. When in operation each would carry a team of two scientists.

The Dyna-4 's central body was constructed of Tomasite in movable, overlapping segments for compactness, but it could be expanded into a long cigar-shaped vehicle for maneuverability in narrow places. The four labs, also cigar-shaped, would fit snugly against the central body when the struts were retracted. Fully equipped with its own pilot-control unit, each capsule was self-operating and could be detached for individual research projects. Passageways in the struts provided easy access to and from the main capsule and smaller labs.

"We got the name Dyna from the Greek word dynamis, which means power," Tom explained. "This is the main power-and-control capsule for the four labs."

"Shucks, Tom," Chow put in, "that's a good name for another reason. This here Dyna Capsule looks like a big dinosaur egg."

"It does, at that," Bud agreed. "A dinosaur egg with wings. I hereby christen thee Egg," he said, aiming a blow at the front end with an imaginary bottle.

"The Egg it is, I guess." Tom laughed. "But let's go and see the real Egg. Remember, this one's only a dummy."

In a huge building the three watched the technicians working on the real Dyna. A gun like device was being fitted into the rear section of the Egg - "What's that they're installing now, Tom?" Bud asked.

"My latest invention - the Insta-Rock gun!" Said Tom.

"Huh?" Chow looked dumbfounded. "What're you gonna shoot?"

"Let me explain." Tom grinned.

"Yeah, please do," Chow said.

"As you both know," Tom began, "seawater contains not just salt, but almost every element in the periodic table is compounded in it. The Insta-Rock gun shoots a special catalyst I've developed that-"

"Hold on a minute," Chow interrupted. "A special what?"

This time Bud explained. "A catalyst is a substance that causes a chemical reaction but doesn't actually take part in it. Right, Tom?"

"You've got it, Bud. Anyway, this catalyst is shot at very high pressure into the water and causes reactions of the calcium and other minerals in the seawater to precipitate insoluble carbonates. This is instant rock."

"Hey, that's brilliant, Tom," said Bud. "You could build yourself a house on the sea floor from nothing but seawater!"

"Purty handy gadget, all right," Chow marveled. "But if you boys'll excuse me, I got to go make lunch."

"Okay, Chow," said Tom. "We're just going to take a look at the tanks where they're pressure-testing the Dyna labs. Then we'll probably go back to my lab."

As the boys headed in the direction of the test tank, Tom said, "Bud, I'll be checking out the Egg in the ocean this afternoon. Want to come along on this little dry - I mean-wet run?"

"Try to leave me home!"

By then the boys had reached the tanks. "How do the tests look?" Tom asked the engineer in charge.

"Very good, Tom. That Tomasite will resist almost any pressure. One thing, though. We're going to need a more powerful magnetic attachment to keep the labs secured to the struts."

"I'll get right on it," Tom promised.

As the boys headed for Tom's lab, the young inventor said, "Why don't we run some tests on that big electromagnet right now, and see how high a pull we can get it to exert?"

"I was just thinking the same thing," Bud replied. "Maybe we can solve that attachment design problem in a hurry."

At the lab the boys hooked up the huge magnet and began checking the force exerted by the device at different current strengths. Just then Chow entered the room with a luncheon tray bearing stainless-steel sizzle platters.

Suddenly the platters leaped from the tray as if by magic and crashed into the electromagnet, splattering food across the lab.

Startled, Chow leaped back. "Jumpin' coyotes! What in tarnation happened?" He asked, bewildered.

"I'm sorry, Chow. That was just our electromagnet. But we've ruined the lunch," Tom apologized as he turned down the magnet.

"Wai, don't worry about that none. I kin rustle up some more. Sure scared me, though," Chow said as they began to take the platters off the magnet.

Tom bent closer to one pole of the magnet. "What's this?" He asked. "It must've been on the floor and the magnet picked it up when we turned it on." He held up a small iron medallion for the others to see.

Looking at the inscription, Bud asked, "What language is that?"

"I'm sure it's Brungarian!" Tom replied excitedly. "Over the years I've learned a little of it. If I'm not mistaken, this says 'good luck.'"

"And that's bad luck for us," Bud said.

"Correct. There definitely is an enemy intruder here at Enterprises! I'd better tell Harlan Ames to make a personnel check and tighten up security precautions." Ames was in charge of the Security Department at Swift Enterprises.

Tom headed for the telephone as Bud and Chow cleaned up the lunch mess on the lab floor. Then Chow left, saying he would "rustle up some more grub."

After lunch the boys loaded the Dyna Egg into the Sky Queen, accompanied this time by Sandra Swift, Tom's sister and special friend of Bud, and her friend Phyllis Newton. Phyl was the daughter of Mr. Swift's lifelong friend Ned Newton, now head of the Swift Construction Company. Since the Dyna Egg was to be taken to Fearing Island for the tests, the teen-age girls had asked to come along and go skin diving.

"Swell," Tom had said when they proposed this. "Bud and I will take our diving gear too and join you when we're through."

Fearing Island was off the Atlantic coast. It was owned by the Swifts and used as a test site, usually for rocket ships.

When the four young people reached the island, Sandy and Phyl disembarked while the boys proceeded to ready the Egg for its first test. Taking the craft beneath the surface, Tom decided to cruise around the island's rocky shores to check the controls and test the ship's maneuverability.

"She's really cool the way she responds to the helm," Tom remarked. "Let's try a little more fine control. I'll work her into that cave over there." He indicated a narrow opening in the rocky wall which was only a little larger than the Egg itself.

"It'll be a tight squeeze, skipper," Bud cautioned. "You sure we ought to take her in this trip?"

"Of course. Why not? We must find out if the controls are as good as they should be. Our lives may depend on it later," Tom replied. He flicked on the autopilot and cut the power. "The Egg should be able to maneuver itself into that cleft."

Bud covered his eyes in mock fear. "Let me know if we make it. Okay?" He squinted and shifted his gaze from Tom to the slim abyss before them.

"Come on, Dyna. Nice and easy does it," Tom said, ignoring his partner's comment. The capsule slipped into darkness.

Suddenly a projection in the cave wall loomed ominously ahead. Before Tom could take any action, the Egg had bumped into it. The impact threw the boys to the floor. Immediately the Insta-Rock gun fired with a roar. Within seconds it began to build up a mountain of thick rock behind them in the entrance to the cave.

Frantically Tom worked the cutoff switch.

"Bud, it won't shut off! We're being sealed into the cave!" He shouted.

CHAPTER IV

GLOWING BUBBLES

FEVERISHLY Tom unlocked the Egg's main power and bus-bar cabinet. It took only a few seconds to find what he was looking for.

"Figured it had to be something like this," the young inventor said to Bud as he reached in, holding insulated pliers. With great care he removed a small length of copper wire. Immediately the Insta-Rock gun stopped working.

Bud whistled. "Don't do that to me again, Tom. There's only a narrow opening left at the cave mouth. Say, what was that you removed?"

"A little by-pass that our Brungarian saboteur - whoever he is-put in to short-out the gun's controls so it would go off at the slightest jar."

The boys donned skin-diving gear and left the Egg. They squeezed their way out of the cave. Breaking the surface, Tom and Bud found themselves only a few hundred yards from the beach where the girls were resting. They had been skin diving along the rocky coast.

"Tom! Bud!" Shouted Sandy as the boys waded ashore. "Where's the Egg?"

The boys flopped on the sand to catch their breath, then described the close call in the cave.

"The Egg's still sealed in down there," Tom told them. "In fact, I must fly back to Enterprises right away and arrange to cut it out. . . . Bud, why don't you stay here with the girls? I'll be back in record time to pick you all up."

Tom had no sooner returned to Swift Enterprises than he was called to the phone.

"Hello?. . . Tom?" Inquired a familiar voice. "This is Harlan Ames. You'll be glad to know we've caught the saboteur. He's a technician who is really a Brungarian agent. The credentials he presented when we hired him were stolen ones."

"Great work! How'd you trap him?" Tom asked.

"It was the good-luck piece you found that alerted us to him," Ames replied. "He'd been snooping in your lab and dropped it by accident. Seems he was working on the Egg this morning and overheard your plans to test it this afternoon. He hoped to ruin the tests by shorting the controls of the Insta-Rock gun."

"He almost succeeded," Tom interjected, and told Ames about his and Bud's narrow escape in the cave. "I flew back to get equipment so we can free the Egg. Good work, Harlan! I hope he was the only spy here."

"I think so, Tom. He has admitted all the recent 'accidents' that have been slowing us up. Anyway, we're being extra careful now. Good luck with the Egg."

"Okay, Harlan," Tom said, and hung up.

Almost immediately the phone rang again. This time it was the Navy Department in Washington.

"The whale has escaped again!" The officer reported. "The dose of tranquilizer that we shot into it wasn't strong enough to put such a huge animal to sleep."

He said that the government, knowing the ingenuity of Tom and his father, wanted them to develop a super but harmless sedative for the whale.

"Then return to the Pacific with it and help in the pursuit of the beast and the stolen vial. But speed is necessary."

"I'll do what I can," Tom agreed, realizing he would have to speed up work on the Egg if he was to take it with him.

And the Egg was still entombed in the cave at Fearing Island!

At once he gave orders for the necessary equipment to release the Egg. Then he issued a directive for his submarine tender to be brought to the spot above the underwater cave.

Tom hastened back to the island in the Sky Queen. Bud, Sandy, and Phyl arrived on the run as he was putting on his diving gear.

"What now, skipper?" Bud queried.

Tom briefed his pal on the results of his several telephone conversations.

"Before we do anything else, we'll rescue the Egg," he finished, handing Bud the diving gear he had dropped on the sand. "Come on, pal. Let's get ready. The sub tender will be out here in a little while."

Upon the ship's arrival Tom and Bud took the special heavy-duty jackhammers and dived to the cave. They set to work with vigor on the rock seal. As soon as the cave mouth had been opened, the boys carefully guided the Egg out into open water. Bud, who was directing surface operations on the ship-to-bottom telephone, hooked a hoist line on the Egg and the craft began its ascent to the surface.

"Oh!" Bud cried out suddenly. "What's-?"

He had been jerked violently upside down! One foot was entangled in the rope and he was being pulled feet first toward the surface with the Egg.

Hurriedly Tom reached for the phone line to order the winch stopped. Bud, who was struggling to free himself, grabbed the line first. It broke!

The situation was extremely dangerous. If Bud were to be pulled up into the air suddenly with all his weight dangling from one ankle he could be seriously injured. Only a minute left before he would reach the surface!

Tom, horrified, swam upward. Passing Bud's struggling figure, he hacked desperately at the line with his shark knife. Finally the line parted!

With the tension removed, Bud's foot came free immediately and he bobbed to the surface. The Egg sank slowly to the bottom.

"You all right, pal?" Tom gasped as they climbed shakily aboard the tender.

"Yes, thanks," Bud panted, "but am I glad you were nearby! You're cool, man, cool!"

As soon as they recovered their breath, the boys went below again and tied a fresh line to the Egg. In a short while the craft was safely secured to the deck of the sub tender.

Tom, Bud, and the girls headed back to Shopton.

"Pretty exciting day," Sandy remarked. She grinned. "I'm glad my friend here isn't going home with one leg!"

Phyl laughed. "Or that my date isn't sealed up in a cave!"

For the next few days everyone at Swift Enterprises worked feverishly to complete the Dyna-4 so that Tom could fulfill his promise to the Navy. The damage to the Egg and Insta-Rock gun was repaired and the new higher-powered magnetic attachment system installed.

Henry Napp and Ben Dodge, the biology team for the Dyna lab, worked to perfect a stronger yet safe sedative to inject into the whale. "Then all you'll have to do, Tom, is track the whale down," Ben said with a grin.

A giant power pincers, which would be used to lift large rock samples, was completed and installed in the geology lab.

The last item to be stored in the completed Egg was a slender, one-man capsule equipped with scientific instruments, useful for investigating niches. It was called the mini-lab.

The day before Tom was scheduled to depart, Mr. Swift called him to his office. As his son entered, the senior inventor was examining what seemed to be a pair of complex oversized goggles.

"What are they, Dad?" Tom asked.

His father grinned. "That, my boy, is Magna Eye, one of my latest inventions. I'd like you to take a few pairs along to the Pacific with you - only it's not entirely perfected yet. You'll have to work out the bugs."

"Sure, Dad. But what's the scoop? I gather this device is some sort of underwater eyepiece, but just what does it do?"

Putting down the goggles, his father said, "As you're well aware, Tom, light is filtered out in water in progressively greater depths at ever shorter wave lengths. The red end of the spectrum disappears first within a few hundred feet. The short blue waves are the last to go.

"Magna Eye is actually an electrooptical system that reduces the frequency of the ultraviolet radiation so that it falls within the visible range. The goggles also intensify any visible light by one thousand times."

"And so, with them on, one can see anything on the ocean bottom clearly," Tom put in. "That's great, Dad. By the way, a lot of the very deep-sea fish have huge eyes. Do you think they could be making use of some principle like this?"

"Could be, Tom," his father replied. "It's certainly worth exploring further."

"I sure can use such a light."

"But Magna Eye," his father went on, "isn't the only new gadget I want you to shake the bugs out of on this trip. This little device here is Magna Ear!"

He handed Tom a small earphone device.

"Basically, this works like Magna Eye - it amplifies high-frequency sounds to within hearing range. Simply adjust this dial and a mini-electronic selector inside will automatically erase any sonic interference as it tunes in to selected vibrations."

"Very ingenious," Tom said admiringly. "You've really been busy, Dad."

Early the following morning the Dyna-4 and her adventurous crew boarded the Sky Queen for the start of their journey. Besides Tom and Bud, the basic crew of the Dyna consisted of Arv Hanson, Hank Sterling, and Chow.

In addition there were two young scientists for each of the four Dyna labs-biologists Ben Dodge and Henry Napp, chemists Don Corey and Bertram Henderson, geologists George Harrison and Dennis Stone, and brothers Jack and Alan Lewis, metallurgists.

Due to the urgency of the mission to recover the vial, there was no time to take the Dyna. On a shakedown cruise. Instead, the Sky Queen flew directly to a small island in the Pacific off the coast of Japan. Because of his previous encounters with Brungarian agents, Tom had decided on the utmost secrecy. The Dyna-4 was launched from the island late at night.

When it was desirable to cruise unseen, a film of dense light-proof oil could be injected between Dyna's Tomasite shells, and removed by a cleansing agent when no longer needed. Tom now released the oil curtain.

He set the craft's monitoring and sensing instruments to keep an automatic watch for both the vial signal and the Brungarian submarine Conus. There was no sign of either, so Tom headed the Dyna for the Mariana Trench. With the craft on autopilot, he set to work debugging the Magna Eye and Magna Ear.

The next day at breakfast Chow announced proudly, "I want you all to know you got a treat aridin' your way. In honor o' this here ex-pee-di-tion, I'm goin' to start servin' a new kind o' grub at meals. A special experiment with deep-sea critters, just like on Cap' n Nemo's ship," he said, alluding to the old Jules Verne novel.

"That's a great idea," Tom grinned, but some of the faces at the table looked a little wary at the prospect.

Bud commented, "Be sure not to grind up the backbones and claws and feed 'em to us!"

Chow sniffed. "You don't trust me, Buddy boy?"

Later, Tom carefully watched the navigational instruments in the control room, while his friend pored over the charts. Suddenly Bud gave a low whistle.

"Wow! Did you see this, skipper? We could hit big trouble!"

"You mean the floating mines?" Tom asked. "I thought you knew about them. They're left over from World War II."

"This whole area is full of them!" Exclaimed Bud. "We hit one of those babies and it's good-by Dyna!"

"Right," said Tom. "Lucky we're cruising deep enough to be safe."

The boys focused their attention on the navigational instruments. Presently the Dyna reached the towering underwater mountain range called the Marcus-Wake Seamounts. Proceeding carefully and scanning the undersea horizons, Tom pointed to a vertical structure.

"There's Dad's new underwater radio tower."

"The one he built for the Navy?"

Tom nodded. "It's on top of a seamount and is an ideal spot because the top comes to within about 120 feet of the surface. But the important thing for us is that the tower means we're close to our base."

Within a short while Tom was guiding the Dyna-4 into the awesome deeps of the Mariana Trench. When the Egg had safely touched down, Tom said, "Let's try out Magna Eye and see what the bottom really looks like."

Turning off all the craft's lights, Tom removed the oil curtain. Outside the now-clear glass hatch, the eternal black of the deep ocean pressed in. Eagerly Tom put on his Magna Eye goggles.

"Bud," he gasped in amazement, "we're surrounded by dozens of huge green glowing bubbles!"

CHAPTER V

MAGNA EAR CLUE

"GREEN glowing bubbles! Fantastic!" Bud exclaimed.

Chow had heard the exclamation in the galley. "Say, have you hombres gone loco?" He shouted over the intercom.

"Come and look!" Tom replied.

Everyone ran to peer out the portholes. Using the Magna Eye goggles, they stared in astonishment.

Biologist Henry Napp was almost beside himself with excitement. "What could they be?" The lanky man kept asking, more to himself than anyone else. "Tom, we must go out and capture some of those bubbles."

"You're right, Henry. Bud and I will try to catch a few," Tom answered.

While the two boys donned Fat Man pressure suits and put on Magna Eye goggles, the crew  extended the Dyna-4 labs. Then Tom and Bud ventured outside into the cold alien depths of the trench. They carried large jars to capture some of the strange phenomena.

Carefully Tom and Bud worked their way toward some of the smaller bubbles. With a sudden rush they swooped down with the jars and captured two of the watery globes.

Instantly the imprisoned dark-green bubbles turned white! At the same time the others retreated.

"Queerest thing I ever saw," Bud muttered. "They're not bubbles. They're some kind of creatures."

Eager to examine their prizes, the boys entered the biology lab. After ordering the oil curtain drawn so that the lights could be turned back on, Tom put the bubbles in one of the two huge Tomasite specimen tanks.

Now they could be seen without Magna Eye. As Tom and Bud and the two biologists watched, the strange formations which had been cowering in the tank's corner gradually turned dark green and floated out into the center of the tank, trailing a faint green tinge behind them.

"Their color changes are fascinating," said Tom. "I think that white must indicate the sensation of fear in them."

"I think so too," Ben Dodge agreed. "Also, notice that darker spot in the center of those translucent bodies. It looks like some kind of nucleus."

"Yes," said Tom. "That must be their life center. There are certainly no organs visible."

"Let's find out what they eat - and how," suggested Henry.

The two biologists collected various marine specimens that they had in the lab-sea worms, baby squid, plankton, and others. All were either ignored or rejected by the bubbles.

During these feeding experiments, Chow, who had been busy with his own "sea specials" until now, came into the lab.

"Why don't you try some o' this chopped seaweed?" The cook urged. "I been usin' it fer a salad."

Looking vaguely uneasy over the prospects of lunch, Henry took the proffered greens.

"Why not?" He said, tossing them into the tank.

Immediately the bubbles streaked for the floating bits of weed and engulfed them in the way that an amoeba surrounds its food.

"Well," said Bud, "now we know how they eat. But why just the seaweed out of all this stuff we've given them?"

"I'll make a guess," Tom commented. "You know seaweed is high in iodine and salt content. Maybe this is what the bubbles need. Possibly their systems require chemicals and minerals directly. Let's test my idea further by dropping some raw minerals in there with them."

Tom went to the metallurgy and chemistry labs for some samples. As he put in small chunks of rock samples, which bore high concentrations of magnesium, titanium, iodine and other elements, the bubbles fairly swarmed upon them. As they engulfed the chunks, the creatures turned an amber color.

"Wai, I'll be a two-toned cow!" Chow exclaimed. "What'd they do that fer?"

"Offhand, I'd guess that amber means pleasure or satisfaction in them," Tom remarked. "I believe they're actually powerful electrochemical systems which dissolve the rocks, absorb the 'food' content, and exude the waste out through the skin. That might account for the greenish tinge we saw in the water."

"It's a pretty good theory, Tom," said Ben. "You're probably right."

"But imagine what terrible enemies they'd make," Tom went on. "They'd just engulf and dissolve their foes!"

Ben nodded. "I've never come across any life-forms like these."

"Neither have I," said Tom. "I have a strange suspicion about them."

At that moment the young inventor was interrupted by a call from Comm-Con, the communications-control center of the Egg.

"We're picking up a signal. Not sure it's from the whale!"

Forgetting the bubbles for the moment, Tom hurried to the control center in the Egg and checked the main computer.

"Attention, all labs," he announced over the intercom. "The Egg is being readied to pursue the vial signal. Prepare for lab retraction." Tom quickly activated the closing mechanism.

Then he programmed the autopilot to take the Egg in pursuit of the signal and to warn him when it had actually picked up something on the scope.

"Arv, take over and call me when we get close," he requested.

Tom knew that using sonar and his aquatomic tracker, a device for detecting evasive undersea objects, the Egg could trace the whale unaided. But he felt safer with Arv in charge.

Tom headed back to the biology lab. On a sudden hunch he picked up Magna Ear and took it along. In the lab he found everyone excited.

"Hey, Tom," called Bud, "look at this! Ben prodded the bubbles with lightly charged electric rods, and they've divided!"

There were now dozens of small bright-green bubble creatures in the tank, hurtling back and forth and bouncing against the sides.

"Incredible!" Tom cried.

Acting on the hunch that had prompted him to bring Magna Ear, he adjusted the instrument to his head. At once the young inventor was almost deafened by high-frequency, interlocking, overlapping pulsations!

"Listen to this, Bud!" He exclaimed, handing the Ear to his pal. "Those hums and squeaks must be coming from the bubbles!"

For half an hour the men in the lab continued to listen to the cacophony of sounds, recording them and making occasional notes. Finally, with rising excitement, Tom called a halt.

"Come on, Bud." He said. "Let's head back to my lab in the Egg. I have a fantastic theory I want to work on."

In his lab Tom studied the recordings he had made, sketching charts and graphs of the patterns. An hour later he flung down his pencil triumphantly.

"It's just as I suspected," he announced to his chum. "These bubble creatures are actually from outer space!"

"What!" Cried Bud. "Outer space! But they're made of water!"

"True," Tom replied, "and I can't explain that yet. But one thing I do know. They communicate by the same geometric code that our space friends do! I thought I heard traces of an interlocking, overlapping pattern distinctly different from the known sonic vibrations of undersea creatures when I first listened with Magna Ear."

"But what are the bubbles doing here?" Bud asked.

"I don't know," Tom answered. "But they're angry about being confined in that tank. I think I'd better try to communicate with them - and quickly! Fortunately we have Dad's and my space dictionary along."

This was an amazing set of geometric symbols which the Swifts had compiled, knowing that the most feasible way for earth men to communicate with beings of other worlds would be through geometric codes.

The two boys were just leaving the lab when a loud alarm sounded over the intercom. From the biology lab Henry Napp shouted frantically!

"Help! Tom! Mayday! Mayday!"

CHAPTER VI

ENMESHED

ANXIETY lent wings to Tom's feet as he and Bud raced to the biology lab. As they opened the door, they were confronted by a weird and terrible sight. A huge green bubble had almost filled the lab!

The supposedly shatterproof Tomasite specimen tank lay broken on the floor, which was awash with gallons of water. Crowded tightly against the wall stood the two biologists.

"What happened?" Tom called, his eyes wide with disbelief at the sight.

"The bubbles gathered and formed one large globe. It began to expand and cracked the tank!" Cried Ben Dodge. "And it'll crack open the lab the same way!"

The unearthly form was indeed growing larger as they watched. It was glowing bright green as if angry.

Quickly Tom dashed past the rapidly expanding bubble into the hatch in the nose of the biology lab. With desperate urgency he spun open the inner door of the air chamber to get rid of the menace.

Just then a renewed cry for help sounded behind him. "Stop this thing!" Ben yelled.

Glancing quickly over his shoulder, Tom could see Ben and his colleague now pinned tightly against the side. The strange and unexpectedly powerful skin of the bubble was crushing them against the Tomasite lab wall!

"Hold on!" Tom cried.

With the inner hatch door open, the bubble began to flow through into the air chamber. Poised cautiously at the lock of the outer door, Tom waited until the green form had almost filled the space. Then quickly he threw the remote-control switch that opened the outer sea door.

Immediately the unwelcome visitor began swooping into the sea. Tom waited until the last of the strange creature's tough jellylike bulk was in the air chamber. Then he slammed the inner door shut, leaped back, and threw the switch that closed the sea hatch.

Ben and Henry were rubbing their bruised ribs and breathing hard.

"Tom, you took an awful chance," Ben said. "The sea could have flooded us all out. But thanks."

Henry added, "You sure played it cool, genius boy."

Tom grinned. "Well," he said, "since the bubble was so tough and flexible, I figured I could use it as a plug and let it flow out at the same time."

Bud heaved a sigh. "It was okay as long as your timing was right opening those doors."

The young inventor looked around the lab. "That bubble certainly made a shambles of this place," he remarked glumly. "I must say, though, its skin is amazing stuff. I never thought anything could crack Tomasite like that, and yet be as pliable as soft rubber!"

Ben Dodge and Henry Napp had started to salvage their equipment and pick up the pieces of the cracked tank. The whole lab was still knee-deep in water, however. At Tom's suggestion, Bud brought the portable model of the spectromarine selector from the main lab to remove it. This machine had been designed to clean barnacles and slime off undersea objects.

"I've been thinking about the bubble," Tom said to Bud as they installed the spare specimen tank in the biology lab. "It's their skin that fascinates me most. Not only did it crack the Tomasite, but it's obviously strong enough to resist the enormous depth pressures under the sea."

"Also," Bud added, "it doesn't explode from inner pressures when brought into the air. Pretty rugged material, I'd say."

"Don't forget its lightness," Tom put in. "When we caught those bubbles, they weighed almost nothing. Remember? Bud, that skin would make perfect diving-suit material! It would weigh practically nothing, yet it could resist the attack of almost any sea creature."

Tom's eyes sparkled as he warmed to his subject. "In fact," he said, "I have the perfect name for it-Sea Skin!"

"Right," Bud said enthusiastically. "Now all we have to do is find out how to make the stuff."

Both boys laughed at their own premature enthusiasm and headed back to Tom's lab. Before they could start any experiments, Chow announced lunch.

Just as the boys finished eating, a signal from Comm-Con brought Tom and Bud on the run. The vial signal from the whale had been picked up loud and clear.

Tom set the Dyna-4 into quick but cautious pursuit to avoid any trap by his enemies. Watching the whale's path on the compass-course screen of his aquatomic tracker, he noted that the huge beast was heading into a deep S-shaped declivity in the floor beneath them.

"He's dropping into that canyon, Bud," Tom said. "I'm afraid if we go after him in the Dyna-4, or even in the Egg by itself, we'll alarm him and he'll take off again. Besides, there wouldn't be much room in that canyon for us to maneuver and sneak up on him with the ship. What say we go down in Fat Man suits and slip up on the old fellow?"

"I'm game, skipper," Bud replied. "How much time do we have?"

"It's hard to say, Bud. Sperm whales can stay submerged for up to fifty minutes. But we don't know how long he has been down already. I think we'd better jump to it."

The boys climbed into their Fat Man pressure suits while a tranquilizer gun was made ready and brought to them. Then they let themselves outside.

"I wish the new sedative had been ready," Tom remarked as they descended into the deep cleft. "We may have the same trouble with this old-style tranquilizer that the Navy did."

Reaching the bottom, the boys started carefully around the bend of the canyon's S. The sea floor at this depth was cold and pitch black, but wearing Magna Eyes, the boys found the eerie and forbidding landscape springing to life around them.

Suddenly the alarm signal sounded in their Fat Man suits!

"Bud," Tom cried, "the Dyna's warning us about something!"

Looking up toward the rim of the canyon Tom saw the reason for the alarm. Hovering above them was the ominous Conus! An intense beam of white light stabbed down into the canyon from the huge black form. Before the boys could move, it had picked them up.

"We're trapped, Bud!" Cried Tom. "I'd better signal the Dyna for help."

As he did, a hatch opened at one end of the Conus and six diving-suited figures swam rapidly down toward the boys. The group divided, three of the swimmers heading off around the curve o£ the canyon.

"Those three must be going after the whale," said Tom. "They have tranquilizer guns. I guess the three with the net are coming after us. Looks as if we might have a fight on our hands!"

The "fight" was somewhat one-sided. Before the Brungarians came near enough to engage, the divers spread their net and dropped it over Tom and Bud. Though they struggled to free themselves, the boys were rapidly hauled up toward the menacing sub.

Tom pulled desperately at the net. He could see the Dyna-4 coming over the canyon's side to rescue them. But they had to get out of the net before it reached the Conus! Then, seemingly out of nowhere, hundreds of green glowing bubbles appeared. The Brungarian divers became panic-stricken.

Utterly unprepared for an attack by this strange enemy, the Brungarians tried to flee. One huge bubble quickly engulfed a diver. As he struggled, the man dropped his hold on the net.

Tom and Bud found themselves flung free and tumbling slowly back toward the canyon floor. Bud whirled dizzily for a moment, then the gyroscopic brain in his Fat Man suit balanced him in an upright position.

He looked around hastily for his friend. When Bud spotted him, he cried out in horror.

A huge bubble was starting to engulf Tom!

CHAPTER VII

DEADLY MINES

QUICKLY Bud grabbed the Brungarians' net, which was drifting down behind them. He flung it over the huge green bubble.

"That'll fix-" he thought, then stared in astonishment.

Instantly the great globe turned white and divided into many small bubbles. They slipped easily through the mesh of the net and fled!

"You okay, Tom?" Bud asked as his friend struggled to an upright position.

"Yes - thanks to you," Tom answered. "But how about that bubble? I never expected it to break up like that, although we did see the smaller ones divide in the lab. Guess we ought to know by now to expect anything from them."

The Egg, under Arv Hanson's capable guidance, had settled down to the boys' level. Tom and Bud scrambled gratefully into the safety of its hatch.

The Brungarians, meanwhile, frightened and disconcerted by the attack of the strange extraterrestrial creatures, had returned to the Conus, which had fled from the area.

"Well, that's one menace out of the way for a while," said Tom, when Arv Hanson told him of the Brungarians' flight. "But what about the whale?"

"The whale, I'm afraid, took off even earlier," Arv replied. "The arrival of the Conus must have alarmed him and he nosed through the water at the top speed possible for his species."

"So we're right back where we started," Bud commented.

"Not quite." Arv laughed. "We're still getting traces of the vial signal. And since I detached the labs so I could guide the Egg down into this narrow canyon, we could take off after the whale now, if you'd like."

"What are we waiting for?" Tom retorted.

He maneuvered the Dyna Egg up out of the canyon. At the flick of a switch, the oval craft extended smoothly into a streamlined cigar-shape, then jetted off in pursuit of the whale. Presently the mammal began to surface. The Egg zoomed up after it and sped along just beneath the surface.

But a moment later Arv exclaimed, "Look on the sonar screen!"

A field of floating objects loomed dead ahead! Mines? Tom submerged the Egg just in the nick of time. The high-speed craft passed beneath the objects, almost grazing the nearest one.

"Whew! What were they?" Bud asked. The Egg had shot past the objects almost before anyone realized their presence.

"I have a hunch they were mines," Tom answered. "We and the whale may have missed being blown to bits by the closest margin. I'm going to check on them."

Bringing the Egg to the surface, Tom carefully circled back to the floating objects.

They were indeed mines! Tom kept the Egg at a safe distance and generated beams of high-intensity acoustic shock waves from his lab. The deadly mines were detonated.

"Now no unsuspecting ship will be blown up by that field," he remarked as the capsule sped away on its original course.

"We may have done a good deed, skipper, but the whale and its signal are both gone," Arv Hanson reported. "The beast is far away."

"He's really traveling these days."

Disappointed, but satisfied that they had done the right thing in stopping to detonate the mine field, Tom contacted Harper in the Navy sub on the undersea radio and told him about the whale and the mine field.

"Don't worry about the whale. He'll turn up again," said the sub commander. "You did a good  job on the mines, Tom. We all thank you for that.

"Since you're in the area, there is one thing more you could do for us. Take a look around the undersea radio tower that your father put up. There have been some strange radio noises and signal interruptions being sent from it lately."

"Will do, Commander," Tom agreed as he signed off.

As he set the Egg on a course in the direction of the radio-tower seamount, Tom briefed the others on his discussion with the sub's commander.

"We'll have to stop and pick up the four labs on the way, of course," he finished.

Back at the rim of the S-shaped canyon, they found the scientists in the four labs taking observations and readings of the surrounding deep-ocean environment. After the labs were secured snugly to the Egg's hull, the once-more-complete Dyna-4 streaked off toward the distant radio tower.

With the craft on autopilot, Tom and Bud headed for the biology lab. Tom was glad to see that it was back in operation once more.

"Tom," Henry Napp said, "we have the new tranquilizer finished. While you were gone, Ben and I, along with Don Corey and Bert Henderson in the chem lab, concentrated on working out the bugs, and we've done it!"

"Great, Henry."

"Let me show you how effective it is," the biologist said.

Going to a large specimen tank, Henry injected only a microgram of the substance into a large grouper. Instantly the huge fish was immobilized.

"Great!" Said Tom.

"We've already figured out the greater quantity needed to knock out a whale or any other large creatures," Henry went on enthusiastically.

"It's a kind of instant sleep," Bud joked. "In fact, how about calling it Kwik-Nap?"

"Sounds good," Henry approved.

"It sure does," said Tom. "Let's hope Kwik-Nap puts that whale to sleep-assuming we catch up with it, that is."

He told Henry and Ben about their pursuit of the mammal and their encounter with the mines, the Conus, and the bubbles.

"Quite an adventure!" Said Henry. "What next?"

"Right now, we're on our way to the radio tower," Tom replied.

The Dyna-4, to avoid detection, had been traveling under its oil curtain. As the craft approached the radio-tower seamount, Tom removed the curtain.

He stared anxiously out of his forward port. There was the tower, all right, but as Tom looked, a huge object slipped away from it. The Brungarian submarine Conus!

Suddenly the top of the seamount exploded in a great cloud of rock and sand. The next moment the Dyna began to rock violently from the shock waves of the explosions.

Gripping the arms of his chair, Tom glanced out and saw the huge steel framework of the tower teeter, then fall forward, straight toward the Dyna.

CHAPTER VIII

ENEMY HOAX

INSTANTLY Tom threw the controls into reverse. The Dyna accelerated rapidly away from the falling tower. The huge structure narrowly missed the craft and crashed down on the sloping side of the seamount.

"Quick work, skipper!" Arv cried. "You really saved our lives that time!"

"It was more luck than anything else," Tom said modestly.

"Oh yes?" Said Bud. "If you hadn't seen that tower start to fall our way, we'd have had it for sure!"

The scare over, Tom said, "I guess I'd better tell the Navy about this."

He contacted Commander Harper by radio and reported the latest calamity.

"We've been afraid of something like this," the officer said. "The Brungarians have been uneasy about this tower since it was erected. They've tried several times to sabotage it, so they finally made it. Too bad. But I'm glad you all escaped.

"What we're most concerned about, though, is the length of time it'll take to put it back up," the officer added. "How long do you figure it would be?"

"If the Navy will okay it," Tom replied, "I can replace it very quickly."

He described the Insta-Rock gun to the sub's commander. "It should do the work in short order."

"Hop to it, Tom, if you think you can swing the job. Don't worry about approval from Washington. I'll take care of that."

The tower structure was relatively undamaged. Using steel cables from Dyna-4's equipment, and the Egg's atomic power, Tom's crew, in Fat Man suits, easily pulled it upright.

Then, with the tower legs held in position, Tom used his portable Insta-Rock gun to build a solid rock foundation. It was time-consuming, because a considerable base of rock had to be built up around the legs. A few hours later, however, the tower was stabilized and in working order. Tom and his men returned their equipment to the Egg, then pulled off their gear.

In his Fat Man suit Chow looked like an oversized Humpty Dumpty. When the cook finally climbed out of it, he kicked the suit away in disgust.

"Consarn contraption!" Chow spluttered. "It's enough to smother a cowpoke what ought to be out on the range anyhow, 'stead o' bein' lassoed underwater!"

The others laughed as he stomped off in his cowboy boots to the galley. Tom contacted Commander Harper on the radio to report the good news.

The officer was dumbfounded. "You can't be serious," he said. "The radio tower is back in place already? Why, it was only a few hours ago that you first told me it had been sabotaged!"

Tom assured him that it was indeed back in operation.

"You have our warmest congratulations on a job well done," Harper responded. "And I can safely say that goes for everybody from our President on down!"

Tom relayed the commander's message to the crew, adding with a grin, "That goes for everybody from Chow in the galley on up!"

A small celebration was held on board the Dyna-4 that night. As a special treat, Chow served a fine dinner of roast beef, mashed potatoes, and apple pie. As he had secretly promised Bud, there was "not one single far-out, oddball deep-sea special!"

Later Tom set the autopilot for the study base location in the Mariana Trench. Then he and all the others turned in for the night, except Hank who was left on watch at Comm-Con. It was nearly midnight when Tom was awakened by his bunk-side buzzer alarm.

"We've picked up the whale's signal," Hank greeted him as he hurried into the communication center. "At least, I think we have. It sounds a little odd, though - the rhythm's a bit different."

Tom listened closely. "Yes, it does sound funny," he agreed. "Maybe its transmitter is beginning to go. The signal has been emitting for a long while. All the more reason to catch the whale in a hurry."

Tom moved the autopilot to track the whale. Soon the signal became stronger. He left Bud at the controls and loaded the tranquilizer guns with the new Kwik-Nap sedative from the biology lab.

Returning to Comm-Con, he discovered that the signal had been pinpointed among a forest of sharp needle-like crags on the floor of a dark canyon.

"Wouldn't you know the whale would pick a spot like that?" Bud commented. With a yawn he added, "He's a cantankerous creature."

Wearing Magna Eye, Tom edged the Dyna-4 cautiously down to the needle rocks and began working toward the signal. Presently he stiffened alertly.

"Bud, look over there," Tom urged, pointing toward a huge dark shape between two towers of rock. "Is that the whale?"

In the next instant his question was answered. The Dyna-4 Capsule was bathed in a brilliant spotlight.

The dark shape was the Brungarian sub!

At that moment a command crackled over the undersea radio: "Surrender or be torpedoed!"

"Don't do it!" Bud whispered.

Without a moment's hesitation Tom shifted the Dyna into its nose-up position. The craft zoomed out of range like a porpoise "walking" on its tail.

The heavier and less maneuverable Brungarian sub, meanwhile, was edging its way out of the treacherous rock needles. Before the Conus could take up pursuit, the Dyna-4 was safely away and heading for its Mariana Trench base again.

"Boy, that was a close one!" Bud said. "Quick thinking, Tom. I never saw the Dyna perform that way before."

"Too bad I had to do it so suddenly," Tom replied. "Better see if anybody was hurt or thrown around."

Bud was back in short order to report that aside from some broken crockery, everything was intact. No one had been hurt, though all were concerned about what had happened.

"One thing's sure, Bud," said Tom. "We'll really have to watch our step when we're tracing that signal. It's obvious the Brungarians finally picked up the signal and have learned to duplicate the pattern almost exactly. The imitation is still not perfect, but you can bet they'll try to improve upon their hoax as time goes on."

He was more eager than ever to track down the enemy sub Conus, and if possible find its base. He chuckled. "Maybe we could bottle it up and keep the sub from pursuing the whale."

"Right. Let's go!" Bud urged.

The boys decided to search the sea bottom. Tom and Bud stationed themselves at the fore and aft ports, beaming huge searchlights into the black depths. There was no sign of the sub and no unusual sightings. It was not until they were only a short distance from the Mariana Trench that Tom called the Dyna-4 to a halt.

"What's up, skipper?" Bud asked over the intercom.

"I've spotted the wreck of an old sailing ship on a coral reef. Maybe we ought to investigate it. There might be something of historical interest inside. Besides, the sea is shallow here. We can go out in our skin-diving gear. Are you game?"

"Let's go!" Bud agreed.

The boys took fish spears and left the Dyna to hover above the reef. They swam expectantly down to the wreck. For a while they explored the outer edges of the ship, marveling at the wild and fascinating beauty of the jagged coral reef.

Moving into the wreck itself, they quickly spotted an old cask, its wood half decayed. With Tom leisurely following, Bud swam over to the keg and reached inside. As he did, Tom caught sight of something that made him quiver. A gaping mouth and rows of vicious needle teeth! A moray eel was about to attack his friend! He raced to warn Bud but was too late. The moray struck out at Bud's bare hand!

CHAPTER IX

SEA CHEST TREASURE

THE sight of the moray striking at Bud's hand and missing it by an inch lent strength to Tom's efforts to reach his pal before another attack. With a swift lunge he drove his spear through the eel's head.

Startled, Bud leaped back, alarm and then relief showing in his eyes even through his face mask. Looking at Tom, his lips formed the words: "Thank goodness!"

The rest of the wreck seemed like an anticlimax after that. The ship and its interior had rotted almost to a point of disintegration.

Finding nothing of interest, Tom signaled, "Let's go back."

Bud held up one finger, meaning, "Wait a minute."

He had just lifted the decaying lid of a sea chest. It almost crumbled in his fingers.

"Anything there?" Tom wondered.

Bud warily reached down. His face broke into a grin as he held up a handful of coins covered with sea moss and handed them to Tom. As Bud stooped to feel for more treasure, Tom scraped the debris off one coin with his thumbnail.

"Gold!" He exclaimed. "Gold coins!"

Bud chuckled as he held up a second lot, transferred it to his chum, and went on a further search. Tom stuffed the coins into his pockets. He too was smiling but suddenly his smile froze.

"Bud!" He cried. "Our air is almost gone!"

His friend could not hear him, so Tom tugged one arm and pointed to the gauge on his tank. Bud's hands were full of coins but he did not wait to look for further treasure. The boys swam back quickly to the Dyna-4.

On board they exhibited their find. Bud said he had picked up all the coins in the chest. The treasure was cleaned in the chemistry lab and every member of the expedition exclaimed in amazement. Bud had indeed found a treasure of antique American coins carried on a clipper ship.

"Say, here's a Liberty Head in good condition," said Hank Sterling, a coin collector. "And an Indian Head! They're worth a lot. This is an astounding find."

Chow looked at Bud. "Wai, I'll be a horned toad. All I ever found was a Buffalo Nickel. Now you kin retire, Buddy boy."

"What!" Exclaimed Bud. "And miss all the fun of getting into tight spots with old genius boy here?"

When the excitement was over, Tom and Bud realized how weary they were. Directly after supper they fell into their bunks for some much-needed sleep, while the Dyna continued toward her base.

Early the next day the craft reached the slopes of the Mariana Trench. Tom set her down on the previously selected site just below the rim.

"We've heard nothing more from the Navy about the whale," Tom told his assembled crew. "We may as well get down to our real business here, at least until the whale's signal is located again.

"Anyway, I'm proposing that we take the Dyna down into the trench and start gathering specimens and samples immediately. We have a tremendous amount of work to do on our own account."

Slowly the Dyna-4 descended into the strange and forbidding cleft. It was an eerie world of utter blackness and enormous pressure.

By the time the craft touched lightly on the silty bottom, the four research teams had donned Fat Man suits. Then, using powerful searchlights, they ventured out into the cold deep to collect specimens.

Tom and Bud had decided to help the geologists, since they needed extra manpower with their rather heavy equipment. They would drill out long cores of rock for fossil strata specimens.

"Wonder what we'll find," Tom said to himself.

The four were drilling in the sloping side of the trench. They had gone only a short distance when Tom became aware of a deep rumbling sound. Instantly he realized that the vibrations of the big drill had caused a disturbance on the undersea slope!

"Landslide!" Tom shouted over the sonar intercom. He, Bud, George Harrison, and Dennis Stone scrambled for safety.

The heavy rock-slide lasted only a minute. When it was over, the beams of their searchlights revealed a yawning hole in the slope, uncovered by the avalanche. From this black and ominous cavern came a series of rapid explosive noises, almost like machine-gun fire!

"Tom!" Bud cried. "What are those sounds?"

"I have an idea," his chum answered, working his way up the rubble-strewn slope toward the hole. "But I'll need a closer look."

Fascinated, Tom stared into the gaping hole, making a few readings on the portable gauges attached to his Fat Man suit.

"It's steam that's causing the machine-gun fire sounds, I'm sure," he said finally. "Something must be producing it at tremendous pressure down there. When the steam's released into the cold seawater, it produces those explosions."

"Number one question is: What's producing the steam?" Bud asked.

"And the second question is: How do we find out?" Asked geologist George Harrison.

Tom smiled. "Simple," he said. "Bud and I will go inside the cave and look! You game, Bud?"

"Ready when you are, skipper."

Despite the protests of the geologists about the extreme dangers involved, the boys were soon working their way cautiously toward the gaping hole. They flashed searchlights into it and proceeded along its short passageway. Presently Tom and Bud found themselves in an enormous waterless cavern. Just below them was a lake!

"Wow!" Bud whispered in awe.

"It's fantastic, all right," Tom agreed. "Looks like a lot of paintings I've seen of Hades or Dante's inferno. Bud, I believe this stuff is boiling brine!"

"Why isn't there any steam?" Bud queried, looking around in puzzlement.

"This is steam," Tom replied. "Only there's no air and it doesn't condense. Because it's under greater pressure than the outside seawater, it bubbles out from the hole. It has to be under greater pressure, of course, or the sea would rush in.

"Bud, do you realize what a find this place is for geologic study?" Tom went on enthusiastically. "It's almost like a hole down through the crust of the earth! Minerals in this cave must be as they were when the earth was forming! Chemists and geologists could spend a lifetime of study here!"

"A lifetime!" Bud grimaced. "Not for me, but I know what you mean."

"We must get a sample of that brine, if that's what it is," Tom said eagerly. "So I guess that means wading in."

He edged his Fat Man suit cautiously forward in the odd waddling gait peculiar to the ungainly but enormously versatile outfit. Bud followed.

They went cautiously down the steep rocky slope toward the edge of the brine, then waded out. Soon their suits were knee-deep in the boiling liquid. Balancing carefully, Tom operated the Fat Man's pantograph arms until a small sample had been poured through a receptacle and into a simple analyzer inside the suit. The lake was indeed briny.

"We'll have to wait until we get back to the lab for a full analysis," Tom said. "This stuff must be loaded with salts of just about every kind. Scientists would have a ball in here - if they could ever manage to work in this heat. Even in this insulated air-conditioned Fat Man suit, I feel as if I'd walked into a furnace."

"You can say that again," Bud answered. "I'd like to wipe the brow of this Fat Man, if-" He stopped suddenly.

"Bud, what's the matter?"

"Tom!" His pal shouted in disbelief. "The legs of your suit are beginning to melt! We must get out of here!"

"If we still can," Tom thought as they began to clamber up the slope out of the lake.

It was a slippery climb and to support himself he knuckled his mechanical hands into the slimy hill. Bud followed.

Once out of the lake, they started up the rocky slope, but the Fat Man legs seemed less maneuver-able than usual. Finally Tom was able to pull himself onto the overhanging ledge.

"You coming, Bud?" Tom asked, making a half turn.

Bud made a grab for the ledge but his metal fingers merely brushed it and slid off.

"Oh no-" Tom cried as he watched his friend's fast drop.

The legs of Bud's Fat Man banged on the slope and the rocks scraped against his suit. Barely a foot from the seething pool Bud stopped. In sheer terror he clung to the slope.

"Hang on, Buddy boy!" Tom called. Quickly and cautiously he climbed down to the waiting figure.

Tom gouged out footholds for Bud who continued to claw the crumbling rock until he secured his balance. The air-conditioning units of their Fat Man suits had weakened and severe heat now bit into the boys' flesh. Doggedly they worked their way up the slope toward the cavern entrance. Tom was thinking, "If we don't make it soon, the cooling system will fail and we'll be finished!"

CHAPTER X

A DIRE WARNING

"WE must make it!" Tom thought wildly as he and Bud clambered frantically up the slope to the cavern's ledge.

When they reached it, both boys sent SOS calls on their intercoms to the geologists waiting outside the tunnel. The heat in their suits had become unbearable.

Bud, in the lead, at last started down the craggy passage to the ocean. But the heat-weakened legs of his Fat Man suit began to bend under him! Alarmed, he leaped forward and grasped the rocks with his pantograph arms. With great effort he pulled himself forward in the direction of the sea.

"Tom," he cried, "see if you can push the legs of my suit!"

Tom staggered after Bud, his Fat Man legs also beginning to buckle. With a desperate motion he grabbed his chum's outstretched legs. Working together, they moved to the sea entrance. Their Fat Man legs were almost useless.

"Whew!" Tom panted. "I thought that was the end of us. We must make it down this side to the ocean and do it fast."

"Ahoy, skipper! Tom, Bud, where are you?" A familiar voice sounded in their intercoms.

"Tom, there's Stony!" Bud almost shouted as geologists Dennis Stone and George Harrison came into view. "Up here, Stony!"

"Looks as if we arrived just in time," said George as they dragged the boys down the passage. "Talk about hot spots! That beats them all!"

"You're telling me!" Bud groaned.

Back once more in the cool comfort of the Dyna-4's Egg, he and Tom quickly recovered. The Fat Man suits, meanwhile, were also "recovering" in the workshop.

"I'm fascinated by that brine lake, Tom," said George Harrison. "It would make a great geological laboratory, if we could only find a way to work in there."

Tom nodded. "But first we will have to invent a heat - and pressure-proof suit-one that's better than the Fat Man gear, which wasn't designed for infernos. Say, maybe Sea Skin will do the trick, once we can find the secret of it."

"Meanwhile," George said, "I have other work to do. Stony and I will want to get some good long fossil cores from the ocean bed."

The two geologists made their way back onto the sea floor and resumed drilling while their colleagues studied undersea life and mineral formations. In a short time, the scientist teams returned to the Dyna with their samples-containers of ooze, chunks of rock, and bottles of strange, weird creatures.

"Quite a haul," Tom commented as he and Bud watched the scientists unload their important treasures.

"It sure is," replied Stony. "But there's one other place where I'd like to gather some specimens. Yesterday, when we were working on the radio tower, George and I spotted a very deep and narrow pit."

"I saw that too," put in biologist Ben Dodge. "I'd like to get down into that hole! It's possible there are forms of bottom-life in there which are extinct at higher levels."

The discussion of the deep pit interested their colleagues. All agreed that samples of rock and ooze from it would be very valuable to them.

"Okay with me," Tom agreed. "We'll up anchor and take the Dyna over to that pit, then."

"Oh no," said Bud firmly, but with a twinkle in his eye. "I want to take care of another pit first."

"Where is it?" Asked Stony, frowning.

"In my stomach," said Bud. "Don't you guys ever eat?"

Tom pretended to be disgusted with such an idea. "Here we are on the verge of exciting scientific discoveries and he's thinking of his stomach," Tom kidded. Then he laughed. "Well, I guess we're all hungry. We'll go to the pit after lunch."

When it was over, Tom put the Dyna-^t on a course for the radio tower and the mysterious pit in the sea bottom. Soon the familiar tower loomed before them in the forward port.

"Down there!" Cried Stony. "That's the pit we were talking about."

Bringing the Dyna-4 expertly down beside a narrow but obviously deep hole in the sea floor, Tom said, "It's too little for the Egg, or for any of the labs, either. We'll have to find some other way to get in there."

Bud had an answer. "What about the mini-lab? That certainly ought to be small enough, and with its Tomasite hull, it should be safe."

He paused, then added, "In fact, since there's only room for one man, I hereby volunteer to go down into that hole."

There was much protest. It was too risky. The scientists insisted that one of them ought to take the chance, if it was going to be done. But Bud pointed out that they all had work waiting in their labs, and he had nothing in particular to do, anyway.

"Okay," Tom said finally. "But for Pete's sake be careful. While you're gone, I'll cruise around and see if I can pick up the vial signal. We'll be back for you in two hours," Tom promised.

"I'll be here waiting, skipper."

Bud climbed into the tiny, cigar-shaped mini-lab and was pushed out through the double hatch. He cautiously guided it down into the dark pit. As he disappeared, Tom set the Dyna on a course designed to comb as much vertical area as possible, in a search for the vial signal.

He had not gone far when Dyna's automatic monitoring equipment flashed a warning that a sonar message was being picked up. Washington to Tom Swift.

"Must be Harper again," he thought and hurried to Comm-Con.

It was indeed the Navy submarine commander. "Tom," he said, "glad we could get hold of you. I have an urgent message for you from Washington.

"The CIA has reported creditable rumors that the Brungarian sub Conus was in its home port recently to be equipped with some new and extremely powerful underwater weapon! Authorities were unable to find out what this invention is, but one thing CIA was sure of: the prime target for the weapon is the Dyna-4! This could become a rough operation!"

Tom smiled grimly, thinking, "They must want to get rid of us pretty badly!"

Aloud he said, "Thanks very much for the warning, Commander. If Conus is in our vicinity, the sonar screen will pick it up immediately. Meanwhile, we still have a lot of other work to do out here."

"Well, keep an extra eye out for those Brungarians!" The sub's commander warned. "We'll be standing by if you need us."

After signing off, Tom turned his attention once again to the search for the signal. As he neared the end of the two-hour period that he had allowed Bud, there was still no trace of the whale.

"I'd better check with Bud," Tom thought. "We can resume our search after he's aboard."

Tom transmitted a code signal to his chum. There was no answer. After repeated attempts with still no reply, he became alarmed.

"What could have happened?" Tom asked himself.

He brought the Dyna-4 around and raced the sleek craft back to the pit area. He called Bud again. No response. Was the mini-lab still in the pit?

A quick survey revealed that the lab was not in the vicinity!

As Tom was debating what to do, he noticed something that gave him additional cause for concern. Lingering in the water was a greenish telltale tinge!

CHAPTER XI

SCARLET TERROR

TOM'S concern over what might have happened to Bud increased. He donned a Fat Man suit and went down to the bottom of the pit. The mini-lab was not there.

"The bubbles must have kidnapped Bud," he decided.

In a panic he returned to the Dyna-4 and reported his suspicions to the rest of the crew.

"Kidnapped!" Chow stormed. "They can't do that to Buddy boy! I'd rather it was a man I could lasso, but them pesky bubbles, you couldn't git a rope around 'em!"

Tom said, "I'm only guessing, of course. We just don't know enough about the bubbles' habits. Maybe they didn't harm Bud - but the bubbles are certainly capable of it. Remember, one of them started to engulf me, Fat Man suit and all. If they did that to Bud and carried him off somewhere-"

"Well, what can we do?" Asked Arv Hanson, spreading his hands in a gesture of helplessness.

"For a start, we can track the bubbles," Tom answered resolutely. "We have Magna Eye and Magna Ear. And we can set the aquatomic tracker to follow that green trace."

"You mean maybe we can contact the bubbles?" Arv asked.

"Yes."

Tom lost no time in setting a course along the green tinge. Using Magna Eye goggles, he and Arv Hanson kept close watch through the forward port.

An excited exclamation from Tom brought Arv to his side on the run. "Look over there!" He cried, pointing.

Ahead of the Dyna and to starboard was a vast undersea meadow. In it were hundreds of the bubble forms. They appeared to be "grazing" at random. Were they eating or just gathering something?

"They seem to be picking things up from the sea bottom," Arv said finally. "Whatever they're after, those creatures are putting it all into that one huge green bubble over there beyond the others."

"I think they're gathering food," Tom declared. "Manganese nodules, perhaps. The sea floor is full of them in certain spots. And you know what raw metals and minerals mean to those bubble visitors."

"But I don't see any trace of Bud or the mini-lab around here," Arv commented. "What do you think?"

Wild and dismaying speculations raced through Tom's mind. How could Bud still be alive if the bubbles had taken him out of the mini-lab? Could he possibly be inside the big green bubble?

"I must communicate with these creatures!" Tom determined.

Using his space dictionary, he worked frantically to develop a geometric formula by which he could ask the big bubble about Bud. While Tom was doing this, the scientist teams watched the "grazing" operations of the bubbles in fascination.

"What a treasure house that field must be!" Mused metallurgist Jack Lewis.

"And not only to science," his brother Alan added. "The crop of manganese nodules in that one meadow alone must be worth a small fortune!"

Presently Tom dashed back into Comm-Con, waving his completed formula and carrying an ultrasonic generator.

"Tom," cried Hank Sterling, "what's all the excitement about?"

"I've managed to work out a formula that I think ought to get across to the big bubble!" Tom said. "What I want to do is code this, feed it into the high-frequency sound generator, and see what happens."

Hank Sterling smiled. "I can't keep up with you," he said, shaking his head. "Well, let's get your generator installed quickly."

He helped Tom fit the unit into an outlet in the hull of the Egg. Then the young inventor began to broadcast his pulsations to the bubbles. Immediately they started to change from a dark-green color to brilliant pulsating green hues!

"Green means anger, and probably excitement too," Tom guessed. "Look! They're swarming around that great big bubble. We certainly stirred them up. Let's see if we're getting any replies."

Quickly fitting Magna Ear into an outside receptacle, Tom bent his attention to decoding any messages from the jumble of high-frequency sounds that came to him. Presently an expression of triumph crossed his face.

"Something got through to them, at least. They want me to come out!"

"Tom, don't go!" Pleaded Hank. "We can't trust these strange creatures. Why not talk to them a bit more?"

"They probably feel the same way about us," Tom replied. "Besides, I must go. They're our only clue to Bud's whereabouts. For all we know, he might be inside that big bubble, mini-lab and all!"

He donned his Fat Man suit and eased himself out into the sea. Immediately he was surrounded by the green forms. They darted menacingly at him, pressing him toward the big bubble.

Tom was amazed at their power. He could not fight them off. As he was forced nearer to the big bubble, it suddenly yawned ominously into a huge opening.

Frantically Tom swung his Fat Man arms and tried to ward off capture by small bubbles which were crowding around him. His efforts were futile.

A moment later the welcome bulk of the Dyna-^f appeared behind Tom, scattering the creatures in all directions. A hatch opened in the Egg's hull and Hank Sterling and biologist Ben Dodge who were in Fat Man suits emerged. Hurriedly they helped Tom back into the safety of the capsule.

"You sure gave us a scare," Hank said as the trio stepped out of their suits.

Ben Dodge nodded agreement. "You can say that again. But I know if we can make friends with those foreigners at all, Tom Swift will be the one to do it!"

"Thanks, Hank, Ben," Tom said. "Those weirdos were pretty intent on getting me into that big bubble and they weren't taking no for an answer."

Tom hurried to Comm-Con. Through the port he watched the myriad bubbles flow into the opening in the large bubble. Then it gradually began to rise.

"Come on!" Cried Tom to his crew. "Let's go! We must chase them and somehow communicate. I'm convinced they're our only chance of rescuing Bud-or, at least, of finding out what happened to him."

"Let's face it, Tom. Bud may be dead!" Arv Hanson said. "I pray he's not, but-"

"I know. But he also may not be. I've got to know!" The young inventor replied. "And the big bubble's our only link right now with the truth."

The Dyna-4 was quickly porpoised in pursuit of the huge globe and its cargo of small ones. As it fled, the strange object continued to rise toward the surface of the Pacific.

With the Dyna close behind, it presently burst out of the ocean depths into the open air, right into the teeth of a raging typhoon!

"Man, what a storm!" Hank exclaimed. "You forget easily in the deeps how variable things can be up here."

Both the bubble and Dyna were buffeted by towering waves.

"Tom!" Arv Hanson suddenly shouted. "I caught a glimpse of an island not far off - and what's worse, a coral reef!"

Hardly had he uttered the words when the big bubble was lifted by a tremendous wave and dashed upon a jagged outcrop in the reef. Crashing down on the razor-edged coral, the seemingly impenetrable creature was torn open on one side.

Instantly it turned white in fear, then scarlet. The creature was in shock!

Tom watched in horror and fascination at the sight. Using his Magna Ear, he could hear weakly shrill high-frequency sounds of distress coming from the bubble. There was no question of a hoax. The strange planetary form was in trouble.

At once Tom made up his mind. He would try to rescue his former adversary!

CHAPTER XII

FISH-HEADED MEN

WITH great care Tom edged the Dyna-4 close to the pounding reef. In the tremendous surge of the sea, it was a perilous operation.

He kept adjusting the strength of the craft's repelatron beams to keep the Dyna from being pounded against the coral.

"This looks like a Mexican standoff, Tom," said Arv Hanson. "We can keep ourselves off the reef, but how do we actually get that bubble away from the coral without going up on it ourselves?"

"I've been thinking about that, Arv, and I admit it's a tough problem," Tom said. "In fact, it may be impossible. But I thought I'd extend the Egg, put it back into the porpoise position, and try to lift the bubble off on Dyna's nose."

Arv whistled in surprise. "That'll take some doing!" He said. "How do you know you can even hold us upright in that surf by the reef?"

"I don't," Tom replied. "But I'm going to try it, anyway."

First he coded a Stand by for rescue message into the ultrasonic generator and beamed it at the stranded bubble. Then he extended the Dyna-4 to its full length so that the nose came to a cigar-shaped point. Tilting the craft upward into the porpoise position, he edged it carefully toward the great mysterious form.

Fighting the constantly changing impacts of the pounding surf with repelatron beams, Tom hooked the nose under the now-limp bubble. Instantly he hit the reverse-speed control. The Dyna-4 scooted backward through the waves with the bubble held high.

Cheers broke out in Comm-Con. "Congratulations, Tom," put in Arv. "I must admit, I had my doubts."

"So did I." Tom smiled in satisfaction.

Far out in deeper water, he lowered the craft beneath the surface, freeing the bubble from its perch. Immediately the injured creature sank toward the sea floor, with the Dyna-4 close behind it.

On the bottom the bubble began to glow its pleasant amber color; the "skin" was obviously self-sealing. While it did this, the smaller bubbles flowed out of it, also glowing with a clear amber hue.

"Say, Tom, why couldn't Mama here repair herself up on the reef?" Arv interposed. "Guess this material isn't totally resistant."

"Not necessarily," Tom replied. "I think the weakened high-frequency sounds indicate the big bubble was in shock."

Remembering that the amber color meant pleasure, Tom listened with his Magna Ear. A riot of high-pitched squeaks and screeches issued from the earpiece. It was obvious that the bubbles were pleased by their rescue.

Encouraged now, Tom beamed his geometric formula at them again. Immediately the forms surrounded the Dyna and responded in a frenzy of ultrasonic noise.

"Gosh!" Murmured Chow, who had come with the rest of the crew to the Comm-Con. "That's enough to break a man's eardrums!"

Listening intently, Tom frantically copied down the messages as swiftly as he could write, then consulted his space dictionary. Finally he turned to the others.

"They did find Bud in that pit," he said. "Seems the great big bubble engulfed him, mini-lab and all, 'ate' his iron ballast, and then cast him afloat in his Tomasite shell on the surface."

Arv cried, "That means Bud might still be alive! But why didn't the big bubble tell us all this the first time you asked it?"

"Didn't get the message then," Tom explained.

"The big bubble thought our expedition was just trying to stop it and the others from gathering manganese nodules.

"But listen! It has offered to lead us to Bud and claims that his capsule will still be giving off traces of that green tinge. It's the same stuff they use to locate one another, by the way.

"Before we go, though, I want to ask them if Bud was injured," Tom said as he turned back to his space dictionary.

After a brief ultrasonic exchange, Tom shook his head. "They just don't know," he said. "Well, at least there's a good chance now. Get ready to leave."

All the smaller bubbles had flowed back into the big one. The Dyna-4, each of its crew wearing Magna Eyes, followed their new-found ally through the depths.

En route, Tom engaged in a constant ultrasonic interchange with the bubble via his geometric formula. Slowly many of the mysteries surrounding the creatures were solved.

They were, he learned, living submarine organisms from an undiscovered planet which was largely water, or more accurately, an electrolyte. Most of the elements were precipitated in this solution, but some-notably manganese, which the bubbles needed in considerable amounts - had been used up. Apparently they had been coming to earth for some time to get it.

"The bubbles have intelligence seated in their electrochemical nucleus or 'brain,' just as we'd suspected," Tom told the fascinated scientists. "And they can either absorb what they engulf - that is, 'eat' it - or they can hold it unharmed. They ate Bud's iron ballast, but the reason they didn't touch Bud was that his 'shell' gave them strange and unpleasant chemical reactions!"

Chow guffawed. "I allus said Bud was tough as a steer to handle. An 'what kind o' vittles is that, anyway? Chemicals! Why, it'd be like drinkin' pizen all the time!"

Everyone grinned and Ben Dodge added, "Bud's 'shell' gave the bubbles a kind of extraterrestrial heartburn!"

"Right." Tom smiled. "And lucky for Bud too. It was the Tomasite hull of the mini-lab that repelled them and saved him! The big bubble gave us a good bit of information. I guess I owe them a little information about us."

Tom turned back to his code-book to resume the "conversation" with the planet creature. But he was interrupted by a loud bellow from Chow.

"Yahoo! Will you look at that!" He said, his eyes growing round as billiard balls.

In reply Tom shot a glance through the view port.

Several yards behind the big bubble was a giant man-eating shark!

Tom immediately coded a warning to the green globe: DANGEROUS SHARK BEHIND YOU. SINK SLOWLY BENEATH SHIP. WILL RESCUE.

But the space creature did not move. Was it frozen in fear? How would it defend itself from the sting of the razor-sharp teeth?

Chow covered his eyes as the smoke-gray fish circled close to the bubble. Tom was glued to the scene.

He took a deep breath, then unexpectedly let out a roaring laugh. "To borrow your phrase, Chow," he said, nudging his companion, "will you look at that!"

The menacing jaws had chopped into the green skin and bounced back, setting the fish on its tail.

"Now I've seen everythin'," Chow blinked. "Nuthin" better than sendin' a critter like that away with its tail between its legs-er-fins!"

Tom was about to agree when a warning signal sounded. An unidentified blip had appeared on the sonar screen.

"More trouble?" Tom thought, worried.

"Whatever was causing the blip was still too far away to identify, but he noted that it was closing fast.

Quickly donning his Magna Eye goggles, Tom turned to the optical viewer. His worst fears were realized. It was the Brungarian sub Conus, and it was approaching the Dyna at breakneck speed!

A harsh, nasal voice sounded over the open sonarphone receiver. "This is the commander of the Conus," it said in heavy-accented English. "We are going to destroy you. We have a new secret weapon which even you cannot escape! Now you will get a taste of it!"

An enormous jet of flame leaped from the Conus at the Dyna-4 In a flash Tom jetted the Dyna away from the fearsome tongue of flame.

At the same time he activated the craft's Octo-Ink screen. Immediately a dense cloud of black fluid enveloped the Dyna-4 and its escape trail.

"Crazy galoot!" Yelled Chow, when they were safely away from the enemy sub.

Tom nodded. "We were lucky. That bragging sub commander was right. We wouldn't have been able to retaliate. I'll have to come up with some kind of counter-weapon. Chances are we won't always be that lucky."

"Meanwhile, what's happened to our bubble friends?" Arv asked.

"I wish I knew," said Tom. "Without them, our chances of finding Bud are slim."

A few miles farther on, Arv's question was answered. The huge bubble was huddled on the bottom, white with fear. Tom, now fluent with his geometrical code and ultrasonic communicator, quickly explained to the creature that the Conus was Tom's enemy also.

"Will you please continue the search for Bud," he requested. "But stay close to my craft and I can give you the protection of the Octo-Ink screen."

The weird form consented and almost in tandem, the bubble and the Dyna-4 continued on the trail.

Chow went off to the galley and somewhat later appeared in Comm-Con carrying a supper snack. Tom thanked him but said he was not hungry.

Chow understood. "You pretty worried about Buddy boy, same as I am, ain't you, Tom?"

"Yes, Chow. We've just got to find him."

Finally the big bubble surfaced, and with it the Dyna-4. Night had fallen, but the moon shone brightly. The surface of the sea was calm. Nearby was a hilly volcanic island with palmetto trees. It had a flat top, indicating a crater. The beach and reef were of coral and lava.

There was something else visible. Fragments of Tomasite gleamed on the shore!

Alarming thoughts whirled through Tom's mind. The fragments were part of Bud's mini-lab, of course. Had he drowned here? Or was he somewhere on the island?

"Only a landing party can answer that," Tom told himself.

He thanked the big bubble for its help, saying that without it they never would have thought of  coming this far. Then the creature sank back into the depths, presumably heading for the manganese field.

Tom, though eager to go ashore, realized the need for caution. Both the island and its reef were menacing. The Dyna circled the land mass completely without finding a break in the dangerous reef.

"Now what?" Hank Sterling asked as they returned to their original position near the Tomasite fragments. The same question was in everyone else's mind.

Just then Tom, who had been scanning under the surface with Magna Eye, gave a shout. "I see a narrow passage in the reef! No need to maneuver the Dyna in there. We could swim through easily. Hank, Arv - let's try it."

"And count me in," Chow insisted.

The four donned skin-diving gear and let themselves out of the hatch into the open sea. In Tom's face mask was a small transistor radio for communication with the Dyna.

Carefully working their way through the passage, Tom and his friends reached the beach, then set off in different directions to comb the island.

Tom was about to head toward the crater when he heard a soft sound, almost a moan. It had come from a nearby grove of trees. Stealthily he crept into the bush.

"Bud!" Tom fairly flew to his pal's side.

Among the trees lay his chum, half-conscious, but alive!

"Huh? What?" Bud moaned.

It was clear he was almost delirious but he managed to say, "Fish-headed men! I was-attacked - by fish-headed men! Watch-out!"

CHAPTER XIII

SUSPICIOUS VISITOR

"FISH-headed men! Bud is really in bad shape!" Tom thought. "Bud," he said aloud, "it's Tom. Don't you know me, old pal?"

Bud, weak from exhaustion and lack of food, muttered brokenly, " 'Course I know you, Tom. But watch out for the fish men. I..."

He lapsed into unconsciousness.

Hurriedly Tom contacted the Dyna-4 biology lab on his intercom radio. "Ben," he said when the scientist answered, "I've found Bud but he's weak and I think he may be injured. Contact Enterprises at once and have them send a company jet plane to the island. I don't dare take Bud out to the Dyna."

In the meantime Hank, Arv, and Chow had returned. They had seen no one. Tom told them of Bud's strange delusion concerning the fish-headed men and of his plan to have Bud taken to a hospital in a company plane.

"Meanwhile we'd better get a fire going and set up a temporary camp on the beach until the plane gets here."

They moved Bud onto the beach and settled down to their long vigil for the jet. Despite the brilliant tropical moon, Tom was uneasy. Once he heard rustling sounds in the shadowy palmetto scrub behind the shore and went to investigate. But he could find nothing.

"I keep getting a creepy feeling that we're not alone here," Tom said restlessly.

"Me too," Arv replied. "What I can't understand is why, if there are hostile people on this island, they haven't captured us."

"Maybe they've been attacked by the bubbles and are afraid of them," Tom suggested.

"And think the bubbles are friendly with us," Arv added.

Despite their apprehension, the evening proved uneventful. Near midnight the jet appeared, and the four hurriedly lighted the guide fires they had prepared. The big plane landed smoothly on the wide beach.

"Easy does it," Tom cautioned as they loaded Bud into the plane. Turning to Arv, he said, "Chow and I will go along. You and Hank will be in charge of the Dyna-4 while I'm gone. We'll be back as quickly as we can."

As he and Chow were leaving, Tom said to Hank, "Think you can keep from starving while Chow is gone?"

Hank said with a grin, "Don't know what the galley will look like when he returns. But at least we won't have any of those octopus and seaweed specials he's been dishing up lately."

"Oh, is that so. . ." Chow began, with a pretense of wounded pride.

"Come on! Let's go!" Tom urged the cook. "They'll really appreciate you by the time we get back with some new supplies." To Hank and Arv he added, "See you at the Mariana base as soon as we can."

It was early the following morning when the big jet arrived in Shopton. Despite his own lack of rest, Tom insisted upon accompanying Bud to the hospital and waiting for the diagnosis.

"He's had a blow on the head, and is suffering from exposure," the doctor told Tom. "But after a little rest and care he'll be all right. Meantime, you could probably use a little rest yourself."

"I feel better already, Doctor," Tom said, relief showing on his face.

With Bud safely in the doctor's charge, Tom went to his father's offices at Swift Enterprises.

"Hello, Tom," said Mr. Swift with delight when Tom entered. "I knew you were bringing Bud back, but I didn't know you'd already arrived. How is Bud?"

"He'll be fine, Dad, after some rest. We went straight to the hospital. Incidentally, we've had a rough time out in the Pacific."

Tom briefed the senior Swift on the details of their search for Bud and their encounter with the Conus and its new secret weapon.

"Dad, we must invent a counter-weapon to ward off that new high-intensity flame jet of the Brungarians. Let's put a team of scientists to work on some variation of repelatron beams."

"Good idea, son. We'll start today."

At that moment the receptionist announced the arrival of a visitor. He was shown in.

"Tom, this is Dr. Victor Dore," Mr. Swift said, rising to greet the distinguished-looking man. "Doctor, my son Tom. Dr. Dore is Professor of Oceanography at Southern University." He asked the caller, "To what do we owe the privilege of your visit?"

The man seemed at a loss as to where to begin. "I made this appointment primarily because a friend who was a patient at the hospital until today told me about Bud Barclay's ordeal on a strange Pacific island."

At this Tom's interest was kindled.

"Not long ago," the professor went on, "I made a trip alone on a small boat in the South Seas. In the shallows at Crater Island I spotted fish-headed men going about underwater."

"What!" The two Swifts cried out simultaneously.

"It's true," Dr. Dore continued. "I investigated further and found that they seemed to be a race of men who had developed gills and could live underwater. But I was afraid to say anything because I thought I wouldn't be taken seriously. For one thing, I wasn't able to get any pictures. You can imagine what the scientific world would say to a claim like that without proof of some kind!"

Tom smiled. "Yes, I certainly can!"

"Anyway, I thought perhaps your friend had seen some of the fish men," the professor said. "If you're going back there you must investigate it and try to get pictures."

"I don't know," Tom replied hesitantly. "We are going back to the Pacific, but it'll be to our base near the Mariana Trench. We have a lot of work to do there. I'll see if we can find the time to make a trip to Crater Island."

After Dr. Dore had left, Tom said to his father, "His story sounds a little fishy in more ways than one." Both smiled wryly at the pun.

"I think we should do some checking up," Tom went on. "It's all too pat that the professor should happen to be here and have a friend in the hospital when Bud was brought in."

Tom put in a long-distance call and talked for several minutes with the dean of Southern University. The young inventor looked perplexed when he hung up.

"Well, there really is a Professor Dore there and he really did make that South Seas trip a few years back - and he is now visiting here on the East Coast. The fish men still sound like a hoax to me, but the professor's account would certainly explain Bud's ravings on the island."

Tom shrugged. "Guess we'd better give the professor the benefit of the doubt and check into Crater Island a little further."

After a bath and breakfast Tom spent most of the day in his lab. Late in the afternoon he took Sandy and Phyl to the hospital to see Bud. They found him looking much better.

"Hi, pal!" Said Tom. "You're your old ugly self again. Looks as if this easy life agrees with you."

"Sure does." Bud laughed. "It could be habit-forming, though. Hi, girls! Sit down, everybody."

After some more joking among the four, Tom said, "Don't get too comfortable, Bud. We must get back to the Dyna project. But right now, tell us what happened to you."

Bud began, "As the bubble started to engulf the mini-lab, it lifted me right out of the pit. I hit my head against the side and blacked out. Next thing I knew I was on the surface in a wild storm-still in the mini-lab."

"That baby saved your life, Bud," Tom said, and reported his communications with the big bubble.

Phyl broke in, "What's all this about 'communicating with a big bubble' and 'a bubble engulfing the mini-lab? Are you out of your minds?"

Both boys laughed, then Tom said, "I forgot that you girls didn't know about our big bubble friend."

He described their discovery of the incredible creatures from space.

"But let's get back to Bud. How'd you land on Crater Island?"

"I don't know, Tom. When the mini-lab crashed on that reef, I lost consciousness again. I must have been washed ashore in the storm. Anyway, I'm lucky I wasn't killed. When I came to again, I was on the beach, surrounded by the fish-headed men."

"Fish-headed men!" Sandy almost shouted. "Oh no! This story gets wilder and wilder."

"Go ahead and laugh." Bud smiled. "I know it sounds crazy, but it's true! When I struggled to sit up, one of them hit me on the head and knocked me out. I don't recall much after that."

"Well, I'm more inclined to believe Bud's story now than when I was on the island," Tom said.

He told the girls and Bud about the visit of Dr. Dore. The others were astounded and all agreed with Tom that the professor's fish-men story sounded very suspicious. Just then a nurse came to say the visiting time was up.

"You take care, Bud," advised Tom. "Doc says you ought to be up and around in a day or so."

Tom took Sandy and Phyl to dinner in Shopton. After a pleasant evening the Swifts dropped Phyl off, then headed for home.

Their mother was excited and worried. "Tom! Sandy!" She cried. "Your father hasn't come home from work yet. And I can't get any answer on his office phone!"

At that moment the automatic alarm signal on their property buzzed loudly. An intruder was on the grounds! As Tom reached the front porch he saw a shadowy figure dart toward a clump of bushes. Tom streaked after him. Sandy followed.

But the intruder disappeared. Had he escaped or was he hiding? The two Swifts combed the grounds, checking every possible hiding place.

Tom broke the silence. "Sandy, where do you figure the guy went?"

No answer. Tom whirled. Silhouetted in the moonlight were two struggling figures.

"Sandy!"

Tom shot across the lawn, shouting for the release of his sister. But Sandy was trapped in two strong arms. Suddenly the man dropped her in a heap. Then before Tom could tackle him, the assailant raced off.

Tears streamed down Sandy's cheeks as her brother slipped a comforting arm about her shoulders. "Oh, Tom, if you hadn't come-" She gulped.

Mrs. Swift, who had heard the commotion, rushed her daughter inside. Tom, meanwhile, had picked up a folded paper on the porch in front of the door. Opening it anxiously, he read the message.

Tom Swift Sr. Had been kidnapped!

CHAPTER XIV

TOM'S TRICK

TOM was stunned. His father kidnapped!

"Something must be done! But what?" Tom asked himself as he entered the house.

"What set the alarm off?" His mother asked.

Tom hated to do so, but he handed over the note. Mrs. Swift and Sandy gasped.

"How dreadful!" Sandy cried.

The note left on the porch gave no instructions, nor did it say when or how the Swifts would be contacted again. Tom felt completely helpless.

Nevertheless, he tried to reassure his mother and sister, as much to calm his own fears as theirs. Tom quickly alerted security at Enterprises, then notified the FBI.

Since there was nothing more that could be done, Tom and his mother and sister settled down to silent, anxious waiting in the Swift home.

An hour later the telephone jangled. In their desperate state of mind, Mrs. Swift and Sandy jumped. Tom ran to answer it.

A gruff voice rasped, "If you want to save your father's life you are to surrender yourself to us - with the Dyna-4. You will therefore bring it back from the Pacific at once. Then further instructions will come to you in a couple of days."

Tom was speechless. His enemy had Mr. Swift! Now they wanted him and the Dyna-4!

"By the way," the man added, almost as an afterthought, "we also have the black vial and are holding it on an unapproachable island. Our scientists there will learn how to duplicate and detonate that explosive. So your search was in vain, Tom Swift!" With a click the line went dead.

As Tom put down the phone, he wondered whether his ominous caller had merely been boasting, and who were "we"? Brungarians? Did they really have his father and the vial? Or was this just a trick to keep him from trailing the whale any further?

Another thought came to Tom. "If they do have the vial, could the" unapproachable island "be Crater Island?"

Suddenly Tom was struck with an idea. Instead of handing over the real Dyna, he would surrender his Dyna dummy! It duplicated the real one exactly, except that the dummy had no power, weapons, or instruments. He would prepare it just enough to make the craft thoroughly convincing to the enemy.

"Nothing to do now but wait," Tom thought, and spent most of the time planning his strategy.

Apparently the Swifts' enemy had decided upon the two-day interim to allow time for the Dyna-4 to be brought back from its Pacific base in the Mariana Trench. Tom, however, did not order its return. Instead, he instructed Ben Dodge, who was now in charge of Comm-Con, to station the Dyna safely outside the sonar range of the Conus's monitor.

The enemy's instructions came two days later. "You will deliver the Dyna-4 tonight at an old dock on the coast of Newfoundland." The caller was the same gruff-voiced man. "I will give you its exact coordinates." He did so and Tom noted them down carefully.

"You must come alone, or your father will not be released! Remember. No double-crossing."

Tom had spent the past two days installing an electropower unit in the Dyna dummy. This could be controlled manually from inside, or by radio signals from Tom's pencil transmitter. It provided the forward thrust of the capsule and could also lock or unlock the dummy's hatches.

It was a grimly determined crew that loaded the mock-up aboard the Sky Queen for the hop to Newfoundland. Tom and the dummy would be put into the sea not far from the designated rendezvous. Then, after scanning the area, a squad of security and FBI men would be parachuted down a few miles inland. They fully expected the Brungarians to attempt kidnapping Tom and were taking every precaution against this prospect.

Three miles from the rendezvous, the Sky Queen deposited the Dyna dummy in the sea with Tom aboard, and flew off to carry out the rest of her mission.

"Well, here goes!" Tom thought.

He sped his craft underwater toward the old dock. He carefully edged up to the pilings and eased the dummy to the surface.

Through the view port he could detect movement on the dock. Five men were slipping out of the shadows.

"Ready to grab me as I emerge from the Dyna!" he said to himself. "This is where I fool 'em."

Taking care not to make a sound, Tom slipped out of the dummy craft through the nether hatch. He remained well beneath the surface and swam along the shore several yards away from the pier. Finally he surfaced and emerged on the rocky beach.

A soft audio vibration sounded from his pencil radio. The tone was very clear.

"That's the signal from Dad's pencil transmitter!" Tom thought excitedly. "I must be getting close to him!"

Homing in on the signal's source, Tom quickly realized that it was coming from an abandoned warehouse behind the dock. With utmost caution he crept up to the ramshackle building.

A low murmur of voices came from the interior. In order to hear the conversation, Tom moved quickly toward a side window in which most of the glass had been broken. But the conversation was too subdued. Tom raised the frame as quietly as he could and climbed inside.

"Oh!" He murmured.

In a corner, tied to a chair and gagged, sat his father!

Tom was overjoyed and the elder Swift also. His son quickly released him and the two started for the window through which Tom had entered.

Their escape was short-lived. The way was blocked by a ring of menacing Brungarians who were closing in on them.

"Looks as if we have a battle on our hands, Tom," his father said grimly.

"Let's give 'em the old one-two, Dad." Tom grinned. "There are two of us, don't forget - and only six of them!"

"That's the spirit, son," Mr. Swift said as the ring closed in.

In the eerie light from the single bulb, the Swifts fought furiously. But soon the superior forces of the Brungarian gang began to wear them down.

Then the door crashed open and several men charged in. They were FBI agents and Harlan Ames's security guard!

In the bedlam that followed, Tom realized that his father was no longer at his side. He swung around just in time to see the senior Swift being forced out the door at gunpoint by a burly brute. He was obviously the Brungarian leader.

"Stop!" R^om cried.

Quickly he dashed through the doorway, and ignoring the gun, leaped full force on the hulking Brungarian. Mr. Swift broke into the clear.

"Run!" Tom shouted.

He tussled briefly on the ground with the kidnapper, who suddenly rolled free and ran desperately for the dock. Tom dogged his heels until the man leaped into the open hatch of the Dyna dummy.

"Tom!" His father shouted. "We can't let him get away with the Dyna!"

"Don't worry, Dad." Tom smiled. "That's only the dummy. And watch."

Whipping out his pencil transmitter, Tom made a quick frequency adjustment and beamed it at the craft. Instantly both hatches were locked and all power on board was killed. The Dyna dummy had become a floating prison. The Brungarian leader was trapped in what he had expected would be his escape vessel!

Mr. Swift chuckled. "Very clever, Tom. I might have known you'd think up something like that."

"Come on!" Tom urged. "We'd better see how Harlan Ames and the FBI are making out with those thugs."

Back at the warehouse the Brungarian muscle-men had been rounded up and subdued. They glared in hatred at their captors.

"Nice going, Harlan," Mr. Swift said as they came into the warehouse. "You've done a fine job."

The FBI got in touch with the nearest police headquarters and presently cars arrived to take the Brungarians to local jails to await trial. The Dyna dummy was reloaded onto the Sky Queen.

"Now if we can only round up the gang in the Pacific," said Tom, as the Swift contingent set off in the Flying Lab, "we can carry on our work in the Mariana Trench undisturbed."

Mr. Swift smiled. "I'm sure you'll have plenty of interference. Those people are ruthless."

Tom nodded. "I hope they haven't captured the whale and absconded with our government's secret vial of explosive."

"I'm sure they haven't," his father said. "If they had, there would have been no need of holding me or trying to kidnap you."

The next evening Tom and Sandy gave a party in celebration of their father's safe return. Bud recovered completely, was his jubilant self again and made the first toast of the evening. His exuberant words brought Chow running from the kitchen.

"Er-excuse me, folks, Mr. Swift, sir," he drawled. "Jest wanted to say whatever Bud here says goes fer me double." He snatched off his ranch-style chef's hat and held it over his heart.

Mr. Swift cleared his throat to keep from laughing. Before he had a chance to say thank you, Chow had replaced his hat, muttered something, and darted out of the room.

"Now what's he up to?" Bud asked. "Not another weird sea special, I hope."

Sandy sniffed the delicious aroma of food. "You're wrong. It smells great."

Shortly Chow reappeared with a large tray of food, his double chins canopied over a new deep-sea extravaganza which he called "Sea Pheasant Under Glass."

"Chow, you've really done yourself proud," Mr. Swift said warmly as he ate. "Your seafood special really is delicious. Sea Pheasant you called it? That doesn't sound like any fish that I know. What kind is it?"

Chow seemed a trifle reluctant to reveal the truth. "Wai," he said, "don't know as I ought to tell you this, but it's really a fish called rattail."

Groans from Sandy and Phyl and slightly horrified gasps from some of the other guests were drowned out in the hilarious laughter of Tom, Bud, and Mr. Swift.

Before it died down Tom excused himself to answer the telephone. It was an urgent call from the communications center at Swift Enterprises.

"We're receiving an SOS from the Dyna-4!" was the startling report.

CHAPTER XV

MIRED LAB

"WHAT'S the rest of the message?" Tom asked.

"You'd better come over here," the operator answered.

Tom told the rest of the group about the summons, then he and Bud rushed to the comunications center.

"We were only able to pick up that one SOS," the operator informed him. "Since then nothing has come through."

Tom tried in vain to pick up further signals from the Dyna-4.

"No luck," he announced at last. "The radio's being jammed."

"And that can only mean the Brungarians!" Bud exclaimed.

Tom agreed. "We should return to the Dyna right away. I'd better see how my new Repela-flame is coming along."

At the lab a development team was working late on the Repelaflame counter-device. Tom's newest invention would outfit Dyna against any future attack by the Brungarian sub Conus and its underwater flame thrower.

"How's it going?" Tom asked anxiously as he and Bud hurried in.

"Great, Tom," said the head engineer. "We're taking the flame's check unit on a final run-through."

"Is it necessary to test it again?" Tom answered. "We got an SOS from the Dyna and we can't afford to wait here much longer!"

The engineer hesitated a moment, then said, "Well, there's no sense in letting a second catastrophe happen. I don't want the Repelaflame to backfire on you, that's all."

"I understand, but how much longer will the tests take?" Tom asked, watching the crew outfit his device.

One man was leaning near the safety-control panel. He shifted his weight and instantly a shower of flames zigzagged against the wall, then wrapped about his arm!

Cries of panic filled the room as he fell to the floor and began rolling out the fiery tongue. A workman raced to the control panel and shut off the release. Tom gave first aid while Bud contacted the emergency squad. Within seconds an ambulance was speeding the injured man to the hospital on the premises.

"Whew! That was a close one. Tom, you and I might have had a taste of those flames," Bud put in.

"Now you see why we can't be too careful," the engineer told them. "Not all of the check unit wires were hooked up when that man threw the switch by accident."

Within a short while the unit was completely wired and the engineer assured Tom he would have no trouble.

"Okay, skipper, you can take her up - I mean - down now!"

"I guess we can trust him," Bud joked.

"Good luck as usual!" The engineer said, smiling.

"That was fast work, fellows." Tom smiled. "Thanks a lot."

Within an hour Tom, Bud and Chow, with the Repelaflame prototype, had boarded a supersonic jet flown by a company pilot. As they sped westward, Tom kept trying to contact the Dyna-4 again on the plane's radio.

Suddenly he looked up in triumph. "Got them!" He cried.

"Arv, this is Tom," he said into the mike. "We're on our way. What's wrong?"

Though the volume rose and fell somewhat, Arv's voice crackled through the receiver.

"The chem lab has fallen off and we can't retrieve it. The Egg had a power failure and all the labs lost their magnetic attachment and dropped off.

"We found the trouble and replaced several parts. Three of the labs came back under their own power and were reattached, but the chem lab was completely short-circuited. It fell into a deep cleft between giant rocks and we can't dislodge it."

To make matters worse, Arv went on, the lab was wedged in hatch down, close to the sea floor. Don Corey and Bert Henderson could not escape!

By now the high-speed jet was nearing the rescue point in the Pacific. Tom, Bud, and Chow scanned the sea, looking in all directions for the Dyna.

"There she is!" Bud shouted, pointing to a tiny speck on the gleaming sea below.

Skillfully the pilot set the big amphibious plane down on the surface. Arv Hanson edged the Egg and the three labs in close to the plane. The newcomers and their cargo of food supplies and emergency equipment disembarked. Then they waved good-by to the pilot.

The big jet had scarcely taken off again on her return trip to Shopton before the Dyna was streaking downward to the trapped chemistry lab.

"We got your SOS back at Shopton," Tom said to Arv. "Then we couldn't pick you up again.

"What happened? It sounded like jamming to me."

"It was!" Arv replied. "The Brungarians - the Conus, I suppose-started jamming almost immediately after we began sending."

Tom looked grim. "That means they also know something's wrong! We'd better get the lab out in a hurry for more reasons than one. The defense against the new Brungarian weapon is ready, but it'll take a while to install it. Of course the first thing to do is rescue Don and Bert."

The lab was indeed wedged tightly in a position which made it difficult to move.

"I see what you mean, Arv," commented Tom. "This'll be one tough job. As a starter let's try using the giant pincers I had made for handling large rock specimens. They're in the geology lab."

The huge pincers were secured to a handling device at the rear of the Egg. Tom could operate the pincers by remote control from inside the Dyna and use the craft's power to give them force and mobility.

With his craft hovering directly over the trapped lab, Tom carefully manipulated the pincers until they grappled the hull of the chemistry lab. Then, gently at first but with ever-increasing force, he pulled upward on the capsule. Slowly it began to rise out of its rocky trap.

"Looks as if you've got 'er, Tom," Bud said excitedly.

Then, to Tom's horror, the pincers slipped off the smooth Tomasite surface of the chemistry lab! Back into the rocky cleft it crashed head-on!

"Good night!" Tom cried.

Now the hatch and air intakes were not merely on the bottom, they were clogged with the soft ooze of the sea floor. The entire crew of the Dyna-4 groaned almost as one man.

Tom was chagrined by his failure, but not for long. Easing the pincers back onto the pointed hull, he started once more to pull upward on the lab. This time, however, it would not move. Not only was the craft wedged in tighter than before, but the thick slimy ooze formed a suction at the bottom!

"Oh, great!" Bud said.

Tom was glum.

"Now I've really fixed things," he murmured. "It's certain we'll never get the chem lab out with the pincers." Then he added, "I'll have to come up with a better idea."

As Tom rummaged through the supply stores of the Dyna in an effort to devise something that would free the trapped men, Hank Sterling came in.

"Tom," he said, "we've managed to jerry-rig the intercom so we can communicate with Don and Bert. They're getting pretty frantic. Their supply of air is diminishing steadily. If we're going to get them out, we must do it now!"

Tom's anguish showed in his face. "Tell them to hold on, Hank," he said. "I have a plan I'm trying to put into operation as fast as I can."

He worked for a few minutes in the Egg's machine shop, then decided to check on the condition of the trapped men and hurried to Comm-Con.

"How are they?" Tom asked Hank as he came in.

"No answer, Tom. I'm afraid-"

"Keep at it, Hank. I have a hunch their transmission hookup may have gone haywire."

"You could be right, but I don't know how we can verify that," Hank said.

Bud opened the control switch box linking the chemistry lab with the Egg. He tried to contact Don and Bert.

"I get static," Bud observed, "but something's blocking their set."

"Keep sending anyway, Hank," Tom put in. "At least we can tell them what's happening on our end and hope they hear us. I'll take the Egg down beside the rocks. We'll carry this long tube-like device I've just rigged up and attach it to the outlet of one of Dyna's jets, then slip it under the nose of the chem lab."

"I see," said Hank. "If we stick the other end into the ooze, we ought to be able to blast the lab out."

"Something like that," Tom replied. "So we'd better prepare the men for impact." Hank nodded.

Tom went to take over the controls and told the rest of his group what he intended to do.

"Sounds good, Tom," put in Arv Hanson. "It really ought to work."

As he started to secure the necessary tubing to the Egg's jet, loud static broke over the intercom from the chemistry lab. Suddenly a harsh, choked voice rasped: "Hurry! Help! Not much-air-left!"

CHAPTER XVI

STING RAY MENACE

WORKING desperately against time, Tom inserted the tube between the rock walls and deep into the soft ooze beneath the nose of the chemistry lab. The entire crew held their breath when Tom turned on the power.

There was a muffled roaring noise as the concentrated jet power roiled the sticky ooze. Then with a tremendous rush of mud and released gases, the craft blew free and upward into the sea. It fell slowly back to safety beside the towering pile of its former tomb.

On board the Egg a cheer arose from the crew. "Yeah!" Chow added, "Yippee! I ain't seen so much excitement since that last roundup I chucked fer in Texas!"

"Nice going, Tom," Hank and Arv both congratulated him. "That was a brilliant idea."

"Our job isn't finished," he cautioned. "The lab's air-filter system is probably still not working right. Come on. Let's get Don and Bert out of there!"

Taking two extra Fat Man suits, Tom and Bud hurriedly donned their own gear and hastened to the muddy but undamaged chemistry lab. Inside, the boys found the scientists sprawled half-unconscious on the deck.

Once inside the Fat Men, Don and Bert breathed deeply. The fresh oxygen supply quickly brought them back to normal. When they were able to navigate, all four emerged through the hatch and made their way to the Egg. They were greeted warmly.

As Tom clambered out of his Fat Man suit, he said, "We have a big job ahead of us, fellows. As soon as we clean up the chem lab and magnetize it to the struts, we'll have to install the Repela-flame units."

Bert asked, "Exactly how do they work?"

"I've used my repelatron principle. Units inside the aft section of the Egg will send out foam through swiveling nozzles on the hull. It will cover the bodies of the Egg and the labs to form a protective coating in case the Brungarians use their flame thrower on us. Units in the fore section will send out repelatron beams to resist the flames. You and Don take it easy while we get things ready."

Everyone else worked energetically to clean up the chemistry lab. Not only was the air filter in need of repair, but much of the soft ooze had been jetted into the lab during the rescue operation.

"Man, what a mess!" Bud muttered as he hauled another bucket of slimy mud to the waste hatch.

"You kin say that agin," chimed in Chow. "I'll never bake another muddy-lookin' chocolate cream pie agin!"

Finally the cleanup job was done and the lab in place. Tom turned his attention immediately to the Repelaflame device.

"This will be a difficult job," he told Bud, Hank, and Arv. "We'll have to split up to work both inside and outside at the same time."

Using the welding and cutting tools, the four turned to the task. First the swiveling nozzles were installed in the outer hull of the Egg. Then the two Repelaflame units were housed in the ends of the Egg. The job took hours and everyone was glad when it was finally accomplished.

"I feel a lot safer now," Bud remarked.

"Yes, we're really prepared for any sudden attack by the Brungarians," Don Corey added.

After they had eaten a hearty meal, Tom announced, "Now for Crater Island and the fish-headed men."

He steered the Dyna-4 toward the mysterious island. "If the Brungarians are there, we can find out whether or not they have the vial of explosive the whale was carrying."

"And I'd like to find those gill men," said Bud. "I want to make sure I didn't dream the whole episode."

Their underwater course to Crater Island led them past the vast manganese field.

"Look, Bud!" Tom pointed. "The bubbles are still there gathering nodules. Let's contact them."

"Okay, now that they're friendly."

The strange creatures broke off their "feeding" to swarm about the Dyna in response to Tom's ultrasonic call.

"We're on our way back to the island that you first led us to," Tom told them. In response the big bubble told him to be careful.

After a further brief exchange the bubbles returned to their mineral-gathering and the Dyna-4 sped on through the ocean depths. A short time later the sonar alarm sounded.

The vial signal had been picked up again!

"How can we be sure?" Bud said a few moments later. "It's kind of weak, as if it were far off. Is that transmission really from the whale or are the Brungarians imitating it again?"

"We can't be sure," Tom replied. "But what puzzles me is why are they bothering to imitate the signal if they have the vial on Crater Island?"

"Let's follow the signal, anyway," Bud urged. "It's leading us in the direction of the island."

The Dyna sped on, carefully tracking the feeble sound all the while. But as they neared the land mass, the ultrasonic sound suddenly vanished!

"Now what?" Tom murmured.

"We're here at Crater Island," Bud answered, "so let's go ashore and solve this riddle once and for all."

"The signal may be a trap," Tom warned.

"I'm aware of that," his friend countered. "Still, we'll have to chance it."

"You're right, Bud. Our only means of finding any answers is right there across that reef."

The two boys donned their skin-diving gear and took sonarphones so they could talk to each other. Tom ordered the Dyna to stand by outside the reef.

"And under no circumstances send in a rescue party," he told Arv, who was in charge, "unless I order it by radio. Above all, I want the Dyna to remain free, ready for battle if necessary. We may possibly need large-scale reinforcements, and you'd be our only chance of getting them. If there's no word from me in twenty-four hours, contact Enterprises for a rescue force."

"What about the Navy?" Hank Sterling asked.

"No," Tom replied. "No help from the Navy. If the Brungarians are on that island - and I suspect they must be-bringing in U. S. Forces might very well trigger an international incident. That in fact, might be just what the Brungarians want and are trying to do."

"I get you."

As soon as the Egg was abreast of the break in the reef, Tom and Bud slipped through the hatch and made their way cautiously through the opening. The Dyna-4 remained outside the reef, submerged a little distance below the surface, with its radio antenna in the air.

The boys made their way shoreward through a weird and marvelous world. The shallow green water was very clear and the myriad strange life-forms of the reef could be seen flitting among the coral and jagged chunks of lava along the sandy bottom.

Tom and Bud walked in the odd slow-motion manner of divers, but it was not long before Bud grabbed Tom's shoulder and pulled him back.

"Down there! You nearly stepped on a huge stingray, old pal!"

The creature, startled, shook the sand from its back and flitted off.

"The fish in this area," Tom remarked, "seem strangely agitated."

The next moment the boys saw a huge fish head on human shoulders rise from behind a lava rock. Just as quickly it ducked down again.

"Ugh!" Bud cried. "I didn't dream up the fish men!"

Warily both boys pressed their way forward.

The incredible fish head reappeared! Then another! And another!

Before Tom and Bud could make a move to escape, the fantastic-looking men fired dart guns. The boys felt the sharp prick of the darts as they found their marks. Tom and Bud lost consciousness.

CHAPTER XVII

MONKEY WORRY

SLOWLY, consciousness returned to Tom, and with it, memory of what had happened in the reef. He started to get up, then realized that his hands and feet were securely bound.

"How dumb can a fellow get!" He berated himself.

Propping himself on one elbow, he looked about him. Bud was beside him, just regaining consciousness. He, too, was bound hand and foot. The boys were lying on the floor of a small wooden hut.

The hot tropical sun sliced in through an open window. From the angle of the sun's rays Tom figured it was about midday. On the window sill sat a small monkey, watching them intently. There was no one else around.

"I suppose we're castaways on Crater Island," Bud joked.

"Yeah." Tom smiled. "And we must be pretty well in the interior. Otherwise they would have gagged us. They figured we couldn't be heard by any friends who might come after us."

"No sense in shouting then." Bud sighed. "By the way, do you still think I was delirious when I was talking about fish-headed men?"

"No," Tom admitted. "They're real, that's for sure-just ordinary men playing a hoax."

"But why such an elaborate hoax?" Bud asked, puzzled. "And why make us prisoners?"

"I don't know." Tom shrugged. "But my guess is that Professor Dore is mixed up in it and his story must have been a lure to trap me."

"In which case," Bud said, "it certainly worked. How are we going to get free?"

Tom looked around the tiny room and spotted a mirror hanging low on the weather-beaten far wall.

"There's one chance," he replied, working his way over to the wall. "I hope nobody's posted outside."

He proceeded to kick the wall with his bound feet until he dislodged the mirror. Tom stiffened as it shattered on the mud-caked floor, hoping none of the enemy had heard the crash. When no one came to investigate the noise, he slipped a sharp piece of glass between his fingers and urged Bud to move over beside him.

"Try rubbing your wrist ropes on this while I hold it firm," he said.

After much straining effort, Bud's hands broke free. Quickly he untied his ankles and freed Tom. Through all this, the monkey looked on in fascination. When the boys jumped to their feet, he began to shriek and chatter loudly.

"Hey, quiet!" Bud rasped at the monkey in a stage whisper. "You're worse than an alarm system, and worse than that crashing mirror."

"He sure is!" Tom agreed. "If there are any of those fish-headed men around, he'll attract them. We'd better get out of here."

"I'm all for that, genius boy."

Tom suggested, "Let's try to find our diving gear. I'd like to use the radio transmitter in mine."

They made a quick search, but did not find their gear. Leaving the ropes where they had fallen, Tom and Bud slipped out of the hut and found themselves in a clearing in the dense bush. No one was in sight, but they heard voices coming from a house at the edge of the clearing.

"Quick!" Tom urged. "Let's listen!"

They moved stealthily across the open space and peered through a window in the rear of the building. Inside, a dozen men were seated around a table. On it lay a pile of rubber fish-head masks!

Bud nudged Tom and nodded toward a corner of the room. Their diving gear lay on the floor.

Among the men in the room were Ignace Sandor and the alleged Professor Victor Dore, who was talking to Sandor.

"In English," Bud thought. "We're lucky."

From the conversation the boys gathered that the "professor" had just arrived in a Brungarian-owned plane, which had taken off again immediately for the United States. From high above came the drone of the departing aircraft.

"Glad to see you, Foster," Sandor was saying.

"So the 'profs' real name is Foster," Tom thought. "He speaks English like an American. He must be an American who is an agent for Brungaria!"

Almost at once Foster and Sandor began to exchange confidences.

"I kidnapped the real Professor Dore to keep the Swifts from discovering my impersonation," Foster said. "He's being held on a boat off the southwest coast of Florida. Don't worry. No one will find him. It's all wild mangrove there, and the boat - the Marlin B-looks like any other fishing boat.

"According to the original plan," Foster went on, "I was to tell my story to the senior Tom Swift and he would certainly relay it to his son. In turn, Junior would investigate the fish-headed men story and be caught. As things turned out, Junior happened to be home because of his friend's injury.

"But what I want to know," Foster said angrily "is why your people kidnapped Mr. Swift after I went to all the trouble to set up the fish-men trap in the first place!"

"Calm yourself, Foster!" Sandor said soothingly. "No use blowing up. There is a faction of the Brungarian government which preferred to try the kidnapping scheme first. When it didn't work, they fell back on the fish-head trap again.

"Incidentally, Foster, we don't have the vial, as you may know. We told young Swift that story as added bait to get him here to Crater Island in case the kidnapping of his father failed. Lucky we did."

Foster seemed mollified. He actually smiled at Sandor. "By the way, what exactly is this place?" He asked. "Aside from just Crater Island, that is."

" 'This place,' as you put it," said Sandor, "is the Brungarian secret headquarters in the Pacific. From here we intend to harass the U. S. Navy secretly and anonymously with the Conus. And what's just as important, we also intend to destroy Tom Swift Jr. Who has become more than a nuisance!"

Foster looked impressed. "But tell me," he said, "when Barclay was washed ashore here and saw the fish men, why didn't you kill him?"

"In the first place," Sandor said sneeringly, as though to a child, "he was nearly dead anyway. But if he survived and friends found him, his story would help to get his buddy to the island - and Tom Swift's the one we were after!"

Tom could feel Bud tensing with anger as he listened.

"Easy, old pal," he whispered. "We'll get 'em yet."

"And now, we have Tom Jr.," Sandor gloated. "This time, we'll order his father to bring the genuine Dyna-4, not the dummy, as ransom - as well as himself."

"You still haven't explained," said Foster, "why you didn't grab him the first time he was here."

The fish men looked at one another. Finally Sandor said, "We may as well admit the truth. There's a queer-looking, almost supernatural, kind of creature in these waters. It looks like a huge green bubble. It swallows people, and - I hate to admit this - but lately it seems to be friendly with Tom Swift. To be honest, at that time we were afraid if we captured young Swift, the creature might harm us or damage the Conus."

Foster snorted. "You sound like idiots," he sneered.

Just then the inquisitive monkey that had scolded Tom and Bud in the hut leaped past their heads and into the room with Sandor and Foster. He was carrying the rope that Tom had cut off Bud's wrists!

The boys watched helplessly as the little animal ran among the men, chattering for attention and toying with the rope. Momentarily diverted, Sandor looked down at it casually, then turned away.

"Whew!" Tom whispered to Bud. "He doesn't seem to recognize that rope!"

The monkey, tired of waiting for a response from the men, finally leaped into a corner with his incriminating toy.

Sandor and Foster resumed their conversation. Brungarian spies, it seemed, had been keeping watch on the U. S. Research team in the Philippines. The Brungarians had informed their government when the vial could be most easily stolen.

After the harpoon had been shot into the whale, they had suggested to their superiors that more men be sent out to track down the whale.

"Actually, the vial's being carried off by the whale was an accident," Sandor said. "When the whaler was hailed by Tom Swift and the Sea Hound, we thought it best to invite him aboard to search. We'd intended to hide the vial by shooting it into the water on a harpoon head and picking it up later.

"The whale just happened to appear then and we decided to catch it at the same time - to kill two birds with one harpoon, so to speak."

He laughed at his own joke.

"You can understand how furious we were when that harpoon head accidentally broke off!"

"How well I remember," Bud whispered to Tom and grinned.

"Well, anyway," Foster said, "the upshot of it all is that the harpoon head with the vial is still in the whale. Meanwhile, what about the two boys? Hadn't we better make sure they haven't escaped?"

"Don't worry," Sandor said smugly. "They're probably still unconscious. That was a powerful sedative in those darts. Besides, they're safely tied up.

"Let me finish bringing you up to date. We had the Conus pulse out a duplication of the whale's signal to lure the Dyna-4 here. And it worked! Our men in those oxygen-bearing fish heads were waiting for the landing party." Sandor laughed. "It included none other than young Swift himself, as we figured. The Conus chased that craft of his, but it got away."

Tom looked at Bud in satisfaction.

"We figure it'll be back again soon," Sandor went on, "and they'll probably try to put another landing party ashore. So it's about time for the sub to go back out after it."

At his command, the men rose and began to file out of the room. Tom and Bud pressed close under the window.

Peering in again, they saw that two burly Brungarians had been left on guard. The monkey remained in the corner.

Quickly the boys weighed their chances of overpowering the guards. "How can we get our gear and contact the Dyna by radio in time to keep it from being captured?" Bud whispered.

Tom replied, "I trust Arv and Hank to be on the lookout for the Conus. And with the Repela-flame, I'm sure the Dyna can handle the sub. Let's see where those fish men have gone."

Tom and Bud followed the Brungarians through the dense jungle of the island's interior. Gradually the land began to rise and it became clear that the men were ascending the cone-shaped crater.

The bush thinned out as they climbed, giving way to twisted rock and lava. The boys could see most of the island now, its jade-green fringe a sharp contrast to the dark blue of the deepening sea beyond it. As they neared the summit, Tom and Bud found it difficult to keep up with the Brungarians without being seen.

"Now what?" Tom muttered. The ring of the crater's summit was bare and windswept.

He did not have long to wonder. The Brungarians went down into the cone. The boys felt it was safe to follow the same trail. As they crept quietly to the rim, the two paused in surprise.

"Look!" Bud whispered.

The men were disappearing into a narrow cleft part way down the inner wall of the crater!

"We mustn't lose them!" Tom said.

He and Bud worked their way downward quickly and soundlessly. The abysmal entrance was dark and ominous.

"Do we follow or not?" Bud queried.

"We have no light," Tom replied, "and that passage may be full of drop-offs and pits."

"Or suppose we stumble in the dark and the Brungarians hear us?" Bud added.

"I know," said Tom, "but I think it's worth the risk. We ought to find out about that sub base, wherever it is. What do you say?"

"Lead on," Bud answered with an exaggerated bow and sweep of his arm.

A bit fearful, the boys edged their way into the unknown fissure.

CHAPTER XVIII

DUBIOUS ESCAPE

FEELING their way cautiously through the dark passage, the boys found that the rocky path led continuously downward. Indistinctly they could hear the voices of the Brungarians ahead of them.

Finally the passage gave way to a dimly lighted cavern. Its walls were lined with radio equipment. As the boys paused at the edge of the big chamber, the men they had been trailing disappeared down a round hole.

"We must be at the top of a chimney in the rock floor," Tom whispered.

When the last man had gone below, he and Bud hurried across the cavern and peered below. Fastened to the wall of the chimney was a metal ladder which led directly to the open hatch of a submarine!

"Can you beat that!" Bud murmured.

As the boys watched, the last man was descending the bottom rungs of the ladder. He went down into the sub, then looked up to close the hatch behind him. Tom and Bud jumped back!

Hearing no outcry, Tom ventured a further peek down the rock chimney. The sub's hatch was closed.

"Whew!" Bud breathed a sigh of relief. "I thought he saw us for sure and we were in for some more rough treatment."

Tom was excited about their discovery. "Bud,-" he cried, grabbing his chum's arm, "it's the Conus, of course, and this is its hidden base. That means there's an underwater entrance from some spot along the shoreline besides the opening in the reef that we know about."

"And that explains how the Brungarians are able to get on and off this 'unapproachable island' so easily!" Bud finished.

"Of course they could always fly in," Tom said. "That's what Foster did, remember? But using the underwater route, they could never be found. Nobody would ever guess they were here."

"Now that we've found the base, shouldn't we warn Hank and Arv?" Bud asked.

"You're right," Tom agreed. "I got so carried away with the discovery, I almost forgot. Come on. Let's get back to that house and see if we can pick up our gear. Bud, those two wrestlers they left on guard looked pretty beefy. How are your muscles today, fellow?"

His pal grinned and flexed his arms. Bulges of strength stood out.

"Don't forget, Tom, the bigger the men are, the harder they fall!"

Since they were now familiar with the jagged interior of the passage, the boys were able to move quickly. Soon the blue horizon of the Pacific came into view over the crater's rim. Moments later Tom and Bud were heading through the dense jungle toward the house at the edge of the clearing.

They peered cautiously through the rear window and discovered that the two guards were not in the room.

"What a break!" Bud whispered as they climbed in.

Quickly the boys retrieved their diving gear with the built - in radio transmitters and turned to leave. At that moment the monkey came through the door and gave an excited cry!

Outside, the voices of the two husky guards could be heard. Tom and Bud dashed for the window and scrambled out, their diving gear in their hands. They were not a moment too soon. As they landed on the ground, the two men entered the room!

"Hide!" Tom whispered.

He and Bud ducked into the cover of the surrounding jungle. The monkey, more excited than ever now, leaped from the window behind them and followed, chattering madly. The boys glared at him in frustration.

"Is it possible that animal's a trained Brun-garian agent?" Tom joked as they tried to avoid the annoying little creature.

"We'd better get rid of him at once," Bud said. "With all that hue and cry the two guards may get curious and follow. And personally I'd rather deal with one monkey than two gorillas!"

Picking up a stone, he threw it in the general direction of the chattering animal, which quickly retreated.

"Thank goodness!" Tom murmured.

The boys remained hidden in the bush for a while, listening intently for sounds of pursuit. When they heard none, Bud urged departure. They picked up their gear and hurried toward the beach.

"Everything looks so beautiful and peaceful," Tom remarked, "it's hard to believe the intrigue that is going on here under the surface."

"Literally under the surface." Bud grinned as they crouched behind the palmettos at the edge of the shore.

Taking care to remain out of sight, Tom sent a radio message to the waiting Dyna-4, warning Arv and Hank of the presence of the Conus in the immediate vicinity.

The answer was, "We're lying far off shore, just beneath the surface. We've already seen the Conus and evaded it."

"I knew we could count on you," Tom said in relief.

"I have some news for you," Arv replied. "We picked up a radio message just a short while ago from the island to the Conus. Seems your escape has been discovered!"

"I'm not surprised," said Tom.

"The guards reported you were missing when they went to check the hut," Arv went on. "They said something about being alerted by a monkey's racket. Know what they were talking about?"

"I'm afraid so," Tom said glumly.

"I knew that monkey was bad news," Bud commented. "Maybe he really is a trained Brungarian agent."

"Well, they know now that we're gone, Bud. So I think we'd better not risk any more radio contact," Tom said, "unless something urgent develops."

"I was thinking the same thing, Tom," Arv agreed. "The Brungarians might very well intercept our messages."

"Right," Tom replied. "Pick us up at the break in the reef an hour after sunset, Arv. We won't radio again, unless there's an emergency here on the island."

With that he signed off.

It was still only mid-afternoon. Tom and Bud settled down to a long and uneasy wait. They made themselves as comfortable as possible in the thick palmetto scrub behind the beach.

The hours dragged by slowly. The boys kept alert for any sound of a search on the island. They amused themselves by watching the frigate birds circling over the island, the red throats of the males distinguishing them from the female frigates. Land crabs scuttled about in the scrub, and numerous small birds rustled through the leaves. But nowhere was there any sound of men on a hunt for them.

"Why haven't they ordered a general alarm and search of the island for us, since they know we've escaped?" Tom wondered aloud.

"Beats me," Bud replied. "It's almost as though they're baiting us. They know we have no chance to escape."

"Except by the Dyna-4," Tom reminded him. "Does that mean that they've caught the Dyna? Or damaged her in some way? The only other alternative I can think of is that they did overhear our conversation with the Dyna and they're just waiting to trap us when we try to leave. I'd like to check with Arv by radio, but I don't dare now."

"We'll just have to take our chances and keep the rendezvous as planned," Bud said, somewhat bleakly. "But I'd give a lot to know what Sandor and Foster are doing right now."

Tom sighed. "All we can do is wait and hope that they didn't overhear what I said on the radio."

"As though we haven't waited long enough already," his pal complained. "And I'm hungry."

It was hot and quiet in the palmetto scrub, while the cool ocean water lay invitingly across the beach. But the boys did not dare venture forth before sunset, even to try catching fish for food. They found some nuts and ate these.

To the restless boys it seemed as if evening would never come. But finally the sun sank. Impatient to start the swim back to the Dyna, Tom and Bud watched the flaming colors of the tropical sunset.

"Won't be long now," Tom said when the last rim of the sun's red disk disappeared in the sea. "Twilight doesn't last long here in the tropics. It'll be dark before we know it."

In the rapidly growing dusk the boys donned their diving gear and made ready to enter the water.

Casting a long look up and down the shore, Tom spoke, "It's time," he said to Bud, and started across the beach.

They slipped quietly into the sea and began swimming underwater toward the break in the reef and their rendezvous with the Dyna-4.

Suddenly eerie lights appeared in the water around them. From behind chunks of lava rock fish-headed men darted out. In a few moments the boys were completely surrounded! Both groaned in dismay.

Though half-blinded by the strong underwater lights, Tom and Bud could see that their adversaries were armed with dart guns. The attackers started to close in!

CHAPTER XIX

THE WATERY TRAP

THOUGH trapped, Tom and Bud nevertheless braced themselves for a fight.

"So the Brungarians did overhear us on the radio," Tom thought. "They were waiting to spring this trap whenever we showed up."

As the fish men closed in on them, Tom got ready to use his waterproofed repelatron wrist watch. But he realized that even with this weapon he could not defend himself long against so many men.

Just then Bud pointed. A colony of green bubbles was surging through the break in the reef!

At sight of the strange creatures, the fish-headed men panicked and scattered into the dark shallows. Tom and Bud grinned. Then, quick to seize the opportunity to reach the Dyna, the boys swam through the coral breach and into the safety of the open sea.

There, immediately below the surface, loomed the welcome form of the Dyna-4. Tom and Bud scrambled through the hatch.

"Man, talk about relief forces arriving at just the right moment!" Bud said happily. "Those bubbles couldn't have timed it better."

The boys stowed their diving gear and hastened to Comm-Con. Joyous shouts of welcome filled the Egg as the crew descended on them.

Chow was enraged when he heard about the boys' experiences. "Blasted Brungarians!" He stormed. "Let me git my hands on those sea-rovin' mavericks! I'll drop' em in the middle of a roundup an 'let 'em git a taste o' their own medicine!"

When the ensuing laughter subsided, Tom said, "Arv, let's take the Dyna out to the deeps before the Brungarians get out here with the Conus."

As the Dyna-4 started off, it was joined by the bubbles, now a friendly pale green. Tom hurried to his ultrasonic communicator. Programming the formula, he thanked the bubbles for their timely arrival which had frightened off the fish men.

"How did you know we were there?" Tom asked them.

"We didn't know," was the reply. "We swam back to the island to see how you had fared since we left you here. When your attackers closed in, a throng of nearby fish made many excited ultrasonic noises. We streamed in to see what was happening, and to find out if you and your friend were in trouble."

"Which we were," Tom put in.

"Our bubble colony will now return to the manganese field, and soon to our own planet," continued the spokesman. "We only wish we were able to find a little of the element you call titanium, but so far we have failed. Your geologists kindly gave us all they had."

"If you'll wait a little longer," Tom promised, "I'll try to get you more."

He was interrupted by an alert from the sonar. Once again they were picking up the whale's signal!

"Great!" Tom exclaimed. "But it will take a little time to reach the beast."

He signed off on his ultrasonic communicator, then set the Dyna-4 in fast pursuit of the transient signal. With the ship on autopilot, Tom and Bud, weak from hunger, headed for the galley.

"Boy, I'm so starved I could eat an octopus!" Bud cried as Chow heaped a concoction on two platters.

Tom laughed. "That may be exactly what you're getting."

"I don't care," Bud replied. "Even one of Chow's seafood specials would be acceptable."

The cook grinned. "That sure is a big admission, comin' from you, Buddy boy."

Tom asked, "What is this?"

"Don't worry about it none," Chow answered. "I'm through with them fancy underwater critters. This here's plain ole Western-style roast beef and potato hash."

"Let me at it!" Bud cried.

There was silence for a while. When conversation resumed, Tom said, "Bud, I've been wondering where the Conus is. Since we didn't see any sign of the fish men while we were watching the beach, my guess is that their sub carried them out from the hiding place in the cave to the open sea. Then they swam in shallow water around to the break in the reef where we were. I can't think of any other explanation."

"You're probably right," Bud agreed. "Boy, am I glad we're out of that nightmare! What say we turn in? I feel as though I haven't slept in a week."

"You took the words right out of my mouth," Tom replied. "But no more nightmares!"

Next morning when he and Bud walked into Comm-Con, Tom slipped on his Magna Ear and picked up the squeaking sounds of the whale.

"We must be close," Tom said.

Bud peered through the forward ports. Suddenly he shouted, "There it is!"

A hundred yards ahead of them, like a creature from another world, loomed the sperm whale's incredible bulk. Both boys gazed at it in awed silence.

But not Chow who had joined them. "Wai, I'll be hornswoggled!" He cried out. "That critter's the biggest cow I ever saw. Even Texas don't grow 'em that size!"

"Tom," called Hank Sterling, who was at the control panel, "there's another signal blipping in from behind us. Sonar's picking up a good-sized object."

"The Conus!" Tom cried. "I'll bet she's trailing the whale also. That doesn't give us much time."

"Time for what?" Bud asked. "Now that we've caught up with the beast, how do you plan to get the vial back?"

"First, we'll have to put him to sleep with our new Kwik-Nap sedative," Tom replied. "Then we'll cut the harpoon head out of him and get the vial. Trouble is, I don't want the Brungarians sneaking up on us just when we're halfway through the job."

Ahead, Tom could see a small ridge of rugged outcroppings on the side of an underwater mountain. He adjusted the magnification on his optical viewer and nodded in satisfaction.

"Over there!" He exclaimed. "That looks like a grotto in the rock. If we could herd the whale in there, we could operate on him in secret. At least we'd have a better chance of doing it unobserved than we would out in the open sea."

"Good thinking," Bud agreed. "But how do we herd the whale into the grotto?"

"Well, Bud," said Torn, grinning at him, "I thought that you and I and a couple of others would just go out in Fat Man suits and urge him along with fish spears!'' Bud sat bolt upright in his chair." Hey! "He said." That's a fascinating idea! Do you think we can really move him along, though-without getting ourselves squashed in the process? He must outweigh us by about a thousand to one!"

"Right," Tom replied. "But we ought to be able to do it. We'll be wearing Fat Man suits, don't forget. And the Dyna-4 will be right there behind us. Say," he added with a grin, "that whale might be a cow. In any case we'll need about two more cowboys. Anybody else want to go?"

"Count me in," said Hank Sterling.

Before anyone else could speak up, Chow's voice rang out. "Me too, Tom! Roundups are my meat anyway, an 'this sure looks like it'll be one whale o' a roundup." He roared with laughter, while there were groans from the crew at Chow's pun.

Tom readily agreed to let the cook accompany them.

Bud could not resist saying, "Chow, if there's one thing worse than your underwater menu, it's your underwater sense of humor!" Chow gave him a withering look.

Tom ordered a large supply of the Kwik-Nap sedative from the biology lab and poured it into the tranquilizer gun. He was careful to pack a large dose of a fast-acting antidote for the tranquilizer.

"Why the antidote, Tom?" Chow wanted to know. "Won't that stuff wear off anyway after a while?"

"Yes, it will," Tom agreed. "But the whale would have drowned by that time."

"Drowned?" Chow repeated incredulously.

"Sure. Whales are mammals, don't forget. If they stay submerged for too long, they drown just like a man does."

Having gathered all their medicines, surgical equipment, and fish spears, the four would-be underwater cowboys donned Fat Man suits and slipped out of the Dyna's forward hatch.

To each man the whale loomed ominous just from sheer size. Carefully the adventurous four approached their quarry.

"Boy, ain't he a mountain, though?" Chow boomed over the intercom.

"Hank," said Tom, "why don't you and Chow go up along one side and Bud and I will take the other. Just sort of prod him along, about mid-section. And above all, watch out for those big tail flukes."

"Will do, Tom," said Hank. He and Chow headed off around the whale, giving its tail a wide berth.

When the four swimmers were sure they had enough room to scramble away before the black whopper could turn on them, they prodded the whale toward the grotto, working gently at first, then with increasing force and confidence. Close behind them, the Dyna-4 cruised slowly. Through the view port the scientists studied their colleagues' adept manipulation of the hulking animal.

"We're winning!" Bud exulted as they gradually goaded the beast to the narrow rocky opening.

Presently Tom yelled over the intercom, "The whale is all the way in! Arv, pick up Hank and Chow and take the Dyna over behind the outcropping. I don't want it to attract the Conus to the grotto. Bud and I will go in alone and tranquilize junior."

"Okay, Tom, but be careful. And sing out right away if you need help," Arv warned.

With the utmost caution Tom and Bud edged their way into the narrow cavern which had a floor of sharp-pointed rocks. The whale left little room for maneuvering in the tight confines. As they worked their way past his tail, the huge flukes started thrashing wildly and flailing against the rock walls!

"Watch out!" Bud cried, and the boys scrambled to avoid the flukes.

The edge of one hit the right arm of Tom's Fat Man, knocking the egg-shaped suit against the cave wall!

"Tom!" Bud shouted in alarm. "Are you all right?"

"I seem to be, Bud. Just knocked the wind out of me, that's all."

As Tom struggled to get his Fat Man to its feet, he added, "But imagine being hit full force with one of those flukes!"

"If you don't mind, I'd rather not imagine it!" Bud replied.

Picking a spot where the outcroppings of the grotto offered them a little protection, Tom shot a dosage of Kwik-Nap into the huge beast. Within seconds the whale was asleep!

"Man, that's great stuff!" Bud exclaimed.

Working against time with his surgical kit, Tom located the broken-off harpoon head and began to cut around it. Skillfully manipulating his mechanical hands and fingers, Tom removed the gadget and separated the vial from it. He placed the highly dangerous container of explosive in the special protective bag he carried.

"Better hurry, Tom," Bud urged.

"Be finished in a minute," Tom answered. "I must close up the wound first."

Just as he finished and was preparing to administer the antidote to the whale, Bud gave a shout of alarm and pointed to the yawning entrance of the grotto. Blocking the narrow space were half a dozen Brungarians in diving suits. At their head stood Sandor, smiling triumphantly.

"At last!" He seemed to say.

Raising a strange-looking hand weapon, he pointed it straight at Tom and Bud!

CHAPTER XX

VICTORY

THE evil grin still on his lips, Sandor pressed the trigger! A narrow white-hot tongue of flame jetted out.

Instantly Tom and Bud leaped to one side and dodged around the whale. Sandor motioned his men forward.

Tom quickly fitted the capsulated antidote into the tranquilizer gun. He poised the medicinal weapon, ready to trigger it.

"They'll get a real surprise when that whale wakes up all of a sudden." He grinned at Bud. "But watch out! That beast could be our own undoing."

Tom fired the fast-acting antidote and instantly the boys backed into a sheltering cleft in the grotto wall. They watched closely.

As quickly as the huge beast had gone to sleep, it recovered. The whale gave a great shudder, then began thrashing violently in the tight confines of the cave. The Brungarians fled for their lives.

Gradually the whale backed out. In moments it disappeared into the murky depths of the sea.

Cautiously Tom and Bud made their way to the waiting Dyna-4.

"I didn't see any trace of the Conus on our return here," Tom remarked as they took off their Fat Man suits. "But it must be around here some place. The Brungarians know the Dyna's hidden in the area and you can bet they're looking for us right now!"

"We'd better get on our way, then," Bud replied. "You still have the vial?"

"Oh, yes, it's here," Tom reassured him. "I'll put the container in the safe until we can turn it over to the Navy."

After this was done, the boys headed for Comm-Con so Tom could report their success to Commander Harper. They were interrupted by the jangle of sonar alarms. Dyna-4 was under attack!

Tom shot back to fore-port controls. Conus was headed directly for them. As it neared the Egg, the enemy fired its underwater flame thrower. The great jet licked out at Tom's craft!

The young inventor fervently hoped that his own counter-device would work properly! He turned on the Repelaflame.

Instantly the Dyna-4 was covered with a layer of protective foam and Repelaflame threw tongues of fire back on the Conus! Excited cheers arose in the Egg's control room. "Man, does it work! And how!" Bud shouted gleefully.

On the sonar screen Tom and the others could follow the Conus escaping into the depths. Quickly setting his aquatomic tracker, he sent the Dyna-4 in hot pursuit.

After a while Tom realized that the enemy sub was not far from Crater Island. Was it heading for the underwater base? If so, with a little strategy he could keep the Conus and its occupants there a long time. Tom was only seconds away from his quarry when the long, slender Brungarian craft slipped into the cave which was not wide enough for the Egg's bulk.

"Ahoy, Tom Swift!" Sandor's voice crackled over the sonarphone. "You'll never catch us!" He jeered.

"Oh yeah?" Bud exclaimed. "Now we're the hounds and you're the fox."

Tom countered with, "Maybe we can't get in, Sandor, but nobody else will be able to either. You have another surprise coming."

As he broke off the sonarphone connection, Tom activated the Dyna-4 's Insta-Rock gun. Methodically he sealed up the mouth of the Brungarian's cave base with instant rock!

"That ought to take care of the Conus," he said with satisfaction. "The Brungarians themselves can get out of the sub easily enough, of course, and go up to the surface by that path through the crater. But now they haven't any way to get off the island! I suppose Brungaria will eventually fly them out, but at the moment, though, they're out of business!"

Bud laughed. "How'd you like to be Sandor explaining this failure to his superiors when they do pick him up?"

Tom grinned and put his craft on course for the bubbles' manganese field. The crew members were in high spirits with the successful recovery of the vial and Dyna-4 's victory over the Conus.

"Well, what now, genius boy?" Bud asked.

"Notify Harper the search is over."

Tom sent the message to the sub's commander, who congratulated the young inventor and said he would come at once to pick up the vial. When he did, there was a brief celebration between the personnel of the two subs, then the Navy craft sped off.

"Where to, Tom?" Asked Bud, who was at the controls of the Dyna-4.

His pal replied, "I think we should get some coordinates on that manganese field and report it to our government. Then we'll head back to our base in the Mariana Trench. We still have a lot of work to do there."

In no hurry now, the Dyna-4 cruised along at a leisurely speed. About halfway back to the manganese field the intercom buzzed.

"This is Stony. Listen! I recall that you were saying earlier you wanted to get some titanium for the bubbles. I've spotted a rock formation which is similar to one where I found that mineral before. If you want to stop, we'll get some of it to test."

"Right away, Stony," Tom replied. "Point out the place."

At Dennis Stone's direction, Tom brought the Dyna-^f to a halt near a large jagged rock formation. The geologists donned Fat Man suits and went outside. Hastily they hacked off some samples, then returned to their laboratory.

Tests proved positive. Titanium was embedded here in concentration!

"That's great news, Stony," Tom said when the geologist gave him his report. "Now we can fulfill the bubbles' request."

He lost no time in putting the Dyna back on course to the manganese field. When the craft arrived at the field, Tom found the bubbles preparing to leave.

He signaled them to wait. After climbing into his Fat Man suit, Tom picked up a portable ultrasonic communicator and a large piece of titanium ore. When he presented it to the bubbles, they glowed amber with delight.

"This is an unexpected surprise," they said to Tom in geometric code. "What can we give you in return?"

"Well," said Tom, "what I would like most, if it can be managed, is a bit of your 'skin.' I would like to study it. If our people can develop something similar for a Sea Skin underwater suit, all of the oceans would be open to us. We could travel underwater to any place we wish to go, regardless of depth or environment.

"My ship is well-equipped with scientists. All four of our labs would work on this project in addition to their regular experiments."

"Consider it done," the bubbles replied.

Eagerly they exuded several small bubbles, which Tom caught in the hands of his Fat Man suit. Then, as the rest of the bubbles flowed into the big one, Tom reentered the Egg.

In a final communication the big bubble said, "Farewell, friend. We must leave now for our own planet."

Slowly it began to rise toward the surface. Tom followed closely in his craft.

With the Dyna-4 resting on the calm surface of the Pacific, its crew watched in fascination as the big green bubble rose into the air and out of sight.

"What an adventure!" Tom murmured.

Bud nodded, then said, "Back to our other job. Mariana Trench, here we come!"

"Not yet, pal," Tom replied. "I want to contact Enterprises first."

"Enterprises! How come, skipper?"

"We can't very well leave the real Professor Dore stranded in that fishing boat off the Florida coast, can we?" He grinned.

"I hate to admit it," Bud said sheepishly, "but in the excitement of the past few days, I'd forgotten all about him!"

Tom got in touch with Swift Enterprises in Shopton and gave the location of the professor's boat. Then he reported all that had happened on the trip since the Dyna-^t had left Fearing Island.

As he signed off, Tom turned to Bud. "I have a cool idea!" He said.

"Another invention?"

Though Tom said No, he was soon to be working on one which produced an exciting adventure in his Cosmotron Express.

"Here is my plan," Tom went on. "It would be inhuman of us not to see that the Brungarian fish men are rescued from Crater Island. Let's take no chances. I'll notify the Brungarian government myself."

Putting up his radio antenna, Tom immediately contacted Brungaria and told them that their great sub Conus was sealed into rock, and that they would have to pick up their fish men marooned on Crater Island.

As Tom signed off, Bud laughed. "Boy, they must really be ticked off at us," he said.

"That's nothing compared to how furious they're going to be!" Tom grinned. "You don't really appreciate the last act of this little play. When I removed the harpoon head and vial from the whale, I detached the signal generator and left it in the beast's body!

"The Brungarians will soon be off on a fruitless and frustrating search - a kind of wild-whale chase!"

THE END

Table of Contents

CHAPTER I HARPOON DANGER

CHAPTER II A RUINED REACTOR

CHAPTER III TELLTALE MEDALLION

CHAPTER IV GLOWING BUBBLES

CHAPTER V MAGNA EAR CLUE

CHAPTER VI ENMESHED

CHAPTER VII DEADLY MINES

CHAPTER VIII ENEMY HOAX

CHAPTER IX SEA CHEST TREASURE

CHAPTER X A DIRE WARNING

CHAPTER XI SCARLET TERROR

CHAPTER XII FISH-HEADED MEN

CHAPTER XIII SUSPICIOUS VISITOR

CHAPTER XIV TOM'S TRICK

CHAPTER XV MIRED LAB

CHAPTER XVI STING RAY MENACE

CHAPTER XVII MONKEY WORRY

CHAPTER XVIII DUBIOUS ESCAPE

CHAPTER XIX THE WATERY TRAP

CHAPTER XX VICTORY