Echoes of the outboard's roaring motor came back from the trunks of palm trees that lined the lagoon's shore as the tiny boat raced across the water. Deirdre was ashen-white. She turned her eyes from the water, and they fell on the round raw places on Terry's leg where the sucker-disks had bruised it horribly. She shuddered. She still had the sensation of being pursued by the monster. Back where Deirdre's spear had finally liberated Terry, startled and convulsive motions continued, followed by a final gigantic splash. Terry drove the boat on at top speed.

The monster sank again in the spot where the lagoon was deepest. It had come from depths where there was no light; from an abyss where blackness was absolute. Now, having lost its victim, it returned peevishly to such darkness as it could secure.

Terry said curtly, as the small boat raced for the Esperance and the wharf, "That creature was driven up from the Luzon Deep into the lagoon to replace the gadget-carrying fish we speared!"

Deirdre stammered a little.

"Your l-leg.... You're bleeding...."

"I'm pretty well skinned in a couple of places," he said shortly. "That's all."

"Could it be poisonous?"

"Poison," said Terry, "is a weapon for the weak. This thing's not weak! I'm all right. And I'm lucky!"

"I'd have jumped over with my spear, if ..."

"Idiot!" said Terry gently. "Never think of such a thing! Never! Never!"

"I wouldn't want to l-live—"

A new reverberating quality came into the echoes from the shore. The pilings of the wharf were nearby, now. They multiplied the sounds they returned. The Esperance loomed up. Terry cut off the motor, the little boat drifted to contact, and Deirdre scrambled to the yacht's deck, and then took the bow line and fastened it. This was absurdly commonplace. It was exactly what would have been done on the return from any usual ride.

"Go tell the others what we found," said Terry. "I'm going to see if there's more than one of those things around."

"Not ..."

"No," he assured her. "I'm only going to use the fish-driving horn."

Deirdre looked at him in distress.

"Be careful! Please!" She kissed him suddenly, scrambled to the wharf, and set off at a run toward the shore. Terry stared hungrily after her. They'd come to a highly personal decision the night before on the Esperance, but it still seemed unbelievable to him that Deirdre felt about him the way he felt about her.

He went forward to set up the fish-driving combination. One part of him thought vividly of Deirdre. The other faced the consequences that might follow if the bolides were not bolides, and if the plastic gadgets and the nasty-sounding underwater hums were products of an intelligence which could make bolides change their velocity in space; which made them fall in the Luzon Deep in the China Sea and nowhere else.

He set up the recorder with its loop of fish-driving hum. He put the horn overboard, carefully oriented to spread its sound through all the enclosed shallow water of the lagoon. He turned the extra amplifier to maximum output, to increase the effectiveness of the noise, and turned on the apparatus.

The glassy look of the lagoon-water vanished immediately. Fish leaped crazily everywhere, from half-inch midgets to lean-flanked predators a yard and more in length. There was no square foot in all the shallows where a creature didn't struggle to escape the sensation of pins and needles all over its body. And these pins and needles pricked deep.

Flying-fish soared crazily, and they were the most fortunate because so long as they flew, the tormenting water-sound did not reach them. But many of them landed on the beach, and even among the palms.

In the spot where blind and snakelike arms had tried to destroy Terry and Deirdre, the lashing and swirling was of a different kind. Something there used enormous strength to offer battle to a noise. The water was whipped to froth. Twice Terry saw those rope-like arms rise above the water and flail it.

This particular sort of tumult, however, appeared only in one spot. So there was only one such creature in the lagoon.

When Davis and the others came down from the tracking station, Terry turned off the horn. He was applying soothing ointment to the raw flesh of his leg.

"There's a monstrous creature out there," he said evenly when a white-faced Davis demanded information. "Heaven knows how big it is, but it's something like a huge squid. It may be the kind that sperm whales feed on, down in the depths."

Others from the tracking station arrived, panting.

"Oh! I'm tired of being conservative!" added Terry fiercely. "I'm going to say what all of us think! There's something intelligent down at the bottom of the sea, five miles down!"

He glared challengingly around him.

"Who doesn't believe that?" he demanded. "Well, the reporting gadgets don't report any more. We killed the fish that carried them. So that whatever-it-is down on the sea-bed has very cleverly sent up something we ignorant savages wouldn't dare to meddle with! We would be terrified. But we'll show it what men are like!"

Dr. Morton said gently, "Perhaps we should notify the Pelorus. The biologists on board there...."

"No!" said Terry grimly. "I have a private quarrel with this monster. It might have killed Deirdre! And Davis already tried to tell those biologists something! Tell them about this, and they'll want proofs they wouldn't look at anyhow. We'll handle this ourselves! It's too important for them!"

"Much too important," said Deirdre firmly. "The shooting stars aren't shooting stars and there's something down in the depths just like Terry says. He's right that we can't consider sharing our world with—beings that come down from the sky, even if they only want our oceans and don't care about the land. He says that we wouldn't get along with creatures that know more than we do, and we would especially resent any space ships coming uninvited to start colonies on our world while we're not advanced enough to stop them! If that's what they're doing, they have to be fought from the very first instant to the very last moment there's one of them hiding in our seas! Terry's right!"

"I haven't heard him say any of those things, young lady," said Morton drily, "but they're true. And I don't like the idea of a sea monster being in the lagoon anyhow. Especially one that tries to kill people. Still, fighting it...."

"There are a couple of bazookas on the Esperance," said Terry sharply. He looked at Davis. "If you're willing to risk the yacht, we can drive the beast aground, or at least to shallow water, with the submarine horn. Then the bazookas should be able to destroy it. Will you take the risk?"

"Of course you'll use the Esperance," said Davis. "Of course!"

"Then I'll want," said Terry, unconsciously taking command, "somebody at the engine and somebody at the wheel. I'll run the horn. But, frankly, if that monster lays one sucker-arm on the Esperance, it may be good-bye. Any volunteers?"

In minutes the Esperance, her engine rumbling, pulled away from the dock. She had on board all her original company except Deirdre—firmly left ashore by her father and Terry—and in addition she carried Dr. Morton and the most enthusiastic amateur photographer of the tracking station staff. He was shaky but resolute, and was hanging about with an imposing array of cameras, for both still and motion pictures. The Esperance's sails were furled and she went into battle under bare poles. Davis was busy manufacturing improvised hand grenades for himself and Morton.

The sun was nearly overhead. Terry asked Morton questions about the lagoon. They finally chose a minor inlet as the place to which the creature must be driven, if possible. There it could be immobilized by the intolerable sound from the recorder. There it could be destroyed.

"I wonder," said Morton wryly, "if I can present a dead giant squid as part of the explanation for my computed orbits for the last two bolides!"

The Esperance moved steadily toward the place where Terry had nearly been killed.

The enterprise was risky. The Esperance was sixty-five feet long. The creature it was to attack was much larger, and if one of its kind had crushed the bathyscaphe, it had sufficient strength and ferocity to make a battle cruiser a much more suitable antagonist. But the true folly of the effort was its purpose.

It all started when a fishing boat—La Rubia—went to sea and caught remarkable quantities of fish, of which four specimens had had plastic artefacts fastened to them. Then Terry began checking on certain noises he heard in the sea which provoked an incomprehensible crowding of millions of fish into a small area, from which they swam down to depths where they could not survive. Now the killing of this squid was supposed to cast a light on the mystery of the nine bolides which had fallen into a particular part of the ocean.

Terry had the undersea horn turned vertically so that it would transmit a blade of sound wherever he aimed it, instead of spreading all through the lagoon. He turned it on.

The water before the Esperance suddenly speckled and splashed from the maddened leaps of fish of every possible size. He turned it off. He aimed it where the ripples showed the presence of something huge beneath the surface. He turned it on again.

There were convulsive writhings. A long tentacle emerged briefly and then splashed under again. The writhings continued. Terry adjusted his aim. Crazy leapings of smaller creatures showed the line of the sound-beam, as tracer-bullets show the paths of bullets from a machine gun. He cut off the sound for an instant and turned it on again at full volume, pointed where the monster must be. There was explosive tumult underwater. Huge arms flailed above the surface. But once again the creature fled.

The Esperance followed slowly, now. The monster had reacted to the stinging sound-beam as if cowed. But it was a deep-sea creature. It did not know how to move when squeezed into a shallow water which hampered its movements. It seemed frightened to discover itself trapped between the lagoon-bottom and the surface. And it was dazzled by the brightness to which it had been driven. Left unattacked, even for an instant, it tried to burrow away from the light, and again it made a dense cloud of mud from the bottom. Then it became quiet, as if hiding.

Grimly, Terry lanced it with the painful noise. The water frothed. Monstrous tentacles appeared and disappeared, and once part of the creature's body itself emerged. It was cornered into a minor inlet, and there the water grew more shallow and the monster did not want to go to where its motions would be even more confined.

It seemed to flow into the deepest part of the miniature bay. It was as if it felt certain of a haven there. When the tormenting noise-beam struck again, the abyssal monster flung itself about crazily. A terrible, frustrated rage filled it. Its arms fumbled here and there, above water and below. It hauled itself upright so that a part of its torpedo-shaped body broke through the surface. The monster was mad with fury. It plunged toward the Esperance, not swimming now, but crawling with all its eight legs in water too shallow to submerge it. Its effort was desperate. It lifted everything from the water, and splashed everything down again, all the while crawling toward its enemy.

Terry saw Nick and Jug steady the aim of their bazookas. Davis ran toward the bow with hand grenades. The huge squid came crawling, and with every foot of advance the pain-noise grew more unendurable. Suddenly the creature uttered a mooing cry and retreated. The cry was like the mooing noise Terry had picked up from the depths.

It went aground. It struggled to climb ashore, to do anything to escape its tormentors. It foamed and splashed....

Despairing, it turned to face its tormentors. Its body reared almost entirely out of the water, now. It sagged flabbily. It reeled as its arms strained. Its eyes rose above the surface, blinded by the light. They were huge eyes. Squids alone, among the invertebrates, have eyes like those of land beasts. They flamed demoniac hatred. A beak appeared, not unlike a parrot's, but capable of rending steel plates. The beak opened and closed with clicking sounds that were singularly horrifying. It snapped at the yacht, which was beyond reach. One of the tentacles wrenched violently at something. It gave. The arm rose above the water. A thorny mass of branched coral flew through the air and splashed close beside the Esperance.

"Shoot!" said Terry, somehow sickened. "Dammit, shoot!"

Nick and Tony aimed closely. The bazookas made their peculiar, inadequate sounds. The bazooka-shells, like small rocket-missiles, sped through the short distance. They struck. Their shaped charges detonated, again with inadequate loudness. They did not explode in a fashion to tear the creature to bits. Instead, they sent lancing flames a thousand times more deadly than bullets into the squid's flesh.

It fought insanely. It uttered shrill cries. Its arms tore at its own wounds, at the water, at the lagoon-bed as if it would rend and shatter all the universe in its rage.

The bazookas fired again and again.

It was the eighth missile from the bazooka which ended the battle. Then the enormous body went limp. Its horny beak ceased to try to crush all creation. But the long, thick, sucker-disked arms thrashed aimlessly for a long time. Even when they ceased to throw themselves about, they quivered and rippled for a considerable period more. And when it seemed that all life had left the gigantic beast, and the men from the satellite-tracking station stepped on the monstrous body, it suddenly jerked once more, in a last attempt to murder.

The squid's body, without the tentacles, was thirty-five feet long. The largest squid, the Atlantic variety, captured before had a mantle no longer than twenty feet. That relatively familiar creature, Architeuthis princeps, came to a maximum total length of fifty-two feet. Counting the two longest arms of this one, it reached eighty. It could not possibly swim in water less than six yards deep. It did not belong in a coral lagoon, but it was there.

It was close to sunset when the last tremors of the great mass of flesh were stilled. Terry was in no mood for eating, afterward. He skipped the evening meal altogether, and paced up and down the veranda of the dining hall, at the satellite-tracking station. Inside, there was a clatter of dishes and a humming of voices. Outside, there was a soft, warm, starlit night. The surf boomed on the reef outside the lagoon.

Deirdre came out and walked quickly into Terry's arms. She kissed him and then drew back.

"Darling!" she said softly. Her voice changed. "How is your leg? Does it still hurt?"

"It's nothing to worry about," said Terry. "I'm worried about something else. Two things, in fact."

"Name one!" said Deirdre, smiling.

"I'd like to get married soon," said Terry ruefully.

"To whom?" she asked, jokingly.

"But I have to have a business or an income first. I think, though, that with a little hard work I can start up my especialidades electrÓnicas y fÍsicas again, and if you don't mind skimping a little ..."

"I'll adore it," said Deirdre enthusiastically. "What else would I want? What's the other thing you worry about?"

"That monster," said Terry with some grimness.

"Pouf!" said Deirdre. "You've killed it!"

"I don't mean that one," said Terry more grimly. "I mean the one that sent it. I wish I knew what it is and what it intends to do!"

"You've already found out more than anybody else even dared to guess!" she protested.

"But not enough. We've stirred it up. It sent small fish in the lagoon here and elsewhere to report back to it. We can't guess what the fish reported, but we know some of it was about human beings. Whatever is down at the bottom of the sea must be interested in men. Remember? It made a patch of foam that swallowed up one ship and all its crew. It's interested in men, all right!"

"True, but...."

"We dropped the dredge, which implied that we were interested in it. The bathyscaphe indicated more interest on our part. To discourage that interest—or perhaps in self-defense—it wrecked the bathyscaphe."

"It, Terry?" asked Deirdre. "Or ellos, they?"

"They," he corrected himself coldly. "We killed the fish that were reporting men's doings from here. That was insolence on our part. So the hum at the lagoon entrance went off and, after two nights, started again—and then this huge squid was found in the lagoon. It should have been able to defend itself against us. It was sent up here because it was capable of defending itself! But we've killed it just the same. So now what will come up out of the depths? And what will it do?"

Deirdre said firmly, "You'll be ready for it when it comes!"

"Maybe," said Terry. "Your father once mentioned an instrument he'd like to have to take a relief map of the ocean bottom. Changed around a little, it might be something we need very badly indeed. The horn we've got is good, but not good enough. I'll talk to the electronics men here."

There was a noise of scraping chairs, inside the dining hall. People came out, talking cheerfully. There was much to talk about on Thrawn Island today. The killing of a giant squid had been preceded by a specific guess that linked it to meteoric falls in the Luzon Deep. Logically, the excitement had grown.

Terry found his electronics specialists, and explained to them the type of apparatus he was interested in. He asked if it was included in the island's technical stores. He wanted to assemble something capable of emitting underwater noises of special quality and unprecedented power. There is not much power involved in sound through the air. A cornet player manages with much effort to convert four-tenths of a watt of power into music. A public-address system for a large area may give out fifteen watts of noise. Terry described a device which could use a small amount of power, serving as a sonar or a depth-finding unit, and then, with the throw of a switch, turn kilowatts into vibrations underneath the sea. If powerful and shrill enough, such vibrations could be lethal.

A technical argument ensued. Terry's demands were toned down to fit the equipment at hand. Then three men went with him to the island's workshop. They took off their coats and set to work.

Three hours later someone noticed an unknown vessel making its way into the lagoon. She was stubby and small, and had short thick masts with heavy booms tilted up at steep angles. Her Diesel engines boomed hollowly, louder than the surf. As she entered the lagoon, a searchlight winked on and flicked here and there. It finally found the wharf where the Esperance was moored.

Men of the tracking station staff went down to the wharf to meet the small row boat that was now coming ashore.

A short, stout, irate fishing boat skipper waved his arms and shouted angrily. What had los americanos done to keep La Rubia from catching fish? Why had they changed the arrangement by which the starving wives and children of La Rubia's crew were fed? He would protest to the Philippine Government! He would expose the villainy of los americanos to the world! He demanded that now, instantly, the original state of affairs be restored!

A fish leaped out of the water nearby. Where it leaped, and where it fell back, bright specks of luminosity appeared. Even the ripples of the splashes glowed faintly as they spread outward. The skipper of La Rubia stared. And now the people of the island realized that the look of the water was not altogether commonplace. Little bluish flames under the surface showed that many fish darted there. There were more fish than usual in the lagoon. Many more. The lagoon had suddenly become a fine place to catch fish. Some care would be needed, of course. There were doubtless coral heads in plenty. But still ...

The skipper of La Rubia abruptly returned to his fury and his protests. La Rubia had gone to the place where she always found fish. Always! There was a humming in the water there, and fish were to be found in quantity. But yesterday the American ship had been there, and also this very yacht! La Rubia stayed out of sight lest the americanos learn her fishing secrets. But it was useless. When the two American ships were gone, there was no longer a humming in the sea and no more fish for the crew of La Rubia to capture for their hungry wives and children. And therefore he, CapitÁn Saavedra, demanded that the americanos restore the previous state of affairs.

Davis would have intervened, but the chubby skipper erupted into wilder and more theatrical accusations still.

Let them not deny what they had done! Fish were always to be found where there was a humming in the sea that las orejas de ellos heard and reported to him. But that humming was not in its former place. It was here! At the entrance of the lagoon! The fish were here, also! Los americanos had moved the fish so the crewmen of La Rubia could not feed their wives and children. Los americanos wished to take all the fish for themselves! But fish were the property of all men, especially fishermen with starving wives and children. So he, CapitÁn Saavedra, would fish in this lagoon, and he defied anyone to stop him.

"Certainly," said Terry. "Seguramente!" He added in Spanish: "We'll lend you a short-wave contact with Manila to make any complaints you please. I'm sure all the other fishing boats will be glad to hear where you've been catching fish, and where you've found the fish have moved to! Calm yourself, CapitÁn, and help yourself to the fish of the lagoon, and any time you want to call Manila we'll arrange it!"

He moved away. He went back to the electronics shop, while Morton and Davis and the others talked encouragingly to CapitÁn Saavedra. Presently they suggested that he accept their hospitality, and the CapitÁn and his oarsmen went up to the dining hall, where they were served dinner, and a more friendly mood developed. In time the CapitÁn said happily that he would wait till sunrise to lower his nets, because he didn't want to risk losing them on the coral heads. A few drinks later the CapitÁn boasted about his own system of fishing, as practised by La Rubia. The starving condition of his crew's wives and children ceased to be mentioned.

In the presence of so accomplished a liar, nobody of the tracking station staff mentioned a giant squid hauled partly, but only partly, out of the water. They suspected that he would not believe it. They were sure that he would top their real feat by an imaginary one. So the four crew-cuts listened politely, and fed him more drinks, and learned much.

In the workshop the most unlikely device Terry'd described took form. In effect, it was an underwater horn which was much more powerful than it looked. Submerged, and with power from a group of amplifiers in parallel, it would create a tremendous volume of underwater noise. That sound would run through a tube shaped like a gun-barrel. It would travel in a straight line, spreading only a little.

The same projection tube could also send out the tentative beep-beep-beep of sonar gear, or the peculiar noise a depth-finder makes. So the instrument could search out a distance or find a target, and then fling at it a beam of humming torment equal to bullets from a machine gun.

It would have taken Terry, alone, a long time to build. But he had three assistants, two of whom were very competent. By dawn, they had it ready to be mounted upon the Esperance. It was placed hanging from the bow, mounted on gimbals, so that it could point in any direction. It was firmly fixed to the yacht's planking.

There was plenty of activity on La Rubia, too, at daybreak. That squat and capable fishing boat prepared to harvest the fish in the lagoon. She got her nets over. She essayed to haul them. Some got caught on the coral heads rising from the lagoon's bottom toward the surface. CapitÁn Saavedra swore, and untangled them. He tried again. Again coral heads baulked the enterprise. The nets tore.

A helicopter came rattling into view from the south. It grew in size and loudness, and presently hovered over the tracking station. Then it made a wide, deliberate circuit of the lagoon. At the inlet where the squid lay almost entirely in the water—but fastened by ropes lest it drift away—above that spot, the helicopter hovered for a long time. It must have been taking photographs. Presently, it lowered one man by a line to the ground. Obviously, the man could not endure any delay in getting at so desirable a biological specimen. Then the helicopter went droning and rattling to the tracking station, and landed with an air of weariness.

La Rubia continued to try to catch fish. They were here in plenty. But the coral heads were everywhere. Nets tore. Ropes parted. CapitÁn Saavedra waved his arms and swore.

The Esperance rumbled and circled away from the wharf, and headed for the lagoon entrance. The singular contrivance built during the night was in place at her bow. She passed La Rubia, on whose deck men frantically mended nets.

The Esperance passed between the small capes and the first of the ocean swells raised her bow and rocked her. She proceeded beyond the reef. The bottom of the sea dropped out of sight. Terry switched on the submarine ear and listened. The humming sound was to be expected here.

It had stopped. It was present yesterday, and even during the night, when La Rubia came into the lagoon. But now the sea held no sound other than the multitudinous random noises of fish and the washing, roaring, booming of the surf.

Deirdre was aboard, of course. She watched Terry's face. He turned to the new instrument, and then dropped his hand.

"I think," he said carefully to Davis, "that I'd like to make a sort of sweep out to sea. It's just possible we'll find the hum farther out."

Deirdre said quickly, "I think I know what you're up to. You want to survey a large area of the ocean while something comes up. Then you can direct that "something" to the lagoon mouth by using your sound device, so the ... whatever-it-is has to take refuge in the lagoon. Since we've killed the squid...."

"That's it," said Terry. "Something like that happened when we speared the fish. The squid took their place. Now we've killed the squid. Just possibly...."

They found the humming sound in the water four miles off-shore. They traced it through part of a circle. If something were being driven upward, it could not pass through that wall of humming sound.

"That proves your point," Davis said. "Now what?"

Without realizing it, he'd yielded direction of the enterprise to Terry, who had unconsciously assumed it.

"Let's go back to the island," said Terry thoughtfully. "I've got a crazy idea—really crazy! I want to be where we can duck into shallow water when we try the new projector."

The Esperance swung about and headed back toward the island. The sea and the distant island looked comfortingly normal and beautiful in the sunshine. Under so blue a sky it did not seem reasonable to worry about anything. Events or schemes at the bottom of the sea seemed certainly the last things to be likely to matter to anyone.

Terry had the Esperance almost between the reefs before he tried the new contrivance. If it worked, it should be possible to make a relief map of the ocean bottom with every height and depth on the sea-bed plotted with precision.

He started to operate the new instrument. First he traced the steep descent from the flanks of the submarine mountain whose tip was Thrawn Island. He traced them down to the abyss which was the Luzon Deep. Then he began to trace the ocean bottom at its extreme depth, on what should have been submarine plains at the foot of the submerged mountain. The instrument began to give extraordinary readings. The bottom, in a certain spot, read forty-five hundred fathoms down. But suddenly there was a reading of twenty-five hundred. There was a huge obstruction, twelve thousand feet above the bottom of the sea, more than twenty thousand feet below the surface. The instrument scanned the area. Something else was found eighteen hundred fathoms up. These were objects of enormous size, floating, or perhaps swimming in the blackness. They were not whales. Whales are air-breathers. They cannot stay too long in deep waters, motionless between the top and the bottom of the sea.

The instrument picked up more and more such objects. Some were twenty-five hundred fathoms from the bottom, and two thousand from the surface. Some were twenty-two hundred up, and twenty-three hundred down. There were eighteen hundred-fathom readings, and twenty-one, and twenty-four, and nineteen. The readings were of objects bigger than whales. They rose very slowly, and appeared to rest, then rose some more, and rested....

Blank faces turned to Terry. He licked his lips and looked for Deirdre. Then he said evenly, "We go into the lagoon. And if we come out again—if!—we leave Deirdre ashore, unless these readings have been cleared up. There are chances I'm not willing to take."

The Esperance headed in. It was not possible for the new instrument to tell what the large objects were. They could be monstrous living creatures, perhaps squids, and one could only guess that their errand was to deal with the surface-creatures—men—who speared fish and giant squids and set off explosions in the Luzon Deep.

Or the rising objects could be, say, bolides which had dived into the Deep from outer space and were now coming to the surface to make sure that the natives of the earth did not again disturb the depths taken over by beings from another planet.