When Terry awoke, next morning, the reflections of sunlight on water came in through the porthole of his cabin. He watched the shimmering contortions of the light spots on the wall. His thoughts went instantly back to the subject they'd dwelt on before he went to sleep. The man with the spectacles—Dr. Morton, but his doctorate was in astronomy instead of medicine—had said that Deirdre and his father had discussed enlisting him in the Esperance's company a month ago. Deirdre'd come into the shop of Jimenez y CÍa. only four days before. Some of the delay could have been caused by time spent in simple sailing from one place to another, mostly on wholly futile errands. They'd gotten a fish-driving paddle at Alua. That'd take some days of sailing each way. Apparently, they'd been fumbling at some vague idea of trying to find out what would produce the facts they'd noted. 'Very queer fish,' Davis had said of some of the catches La Rubia had made. The abyssal fish mentioned last night would be very queer fish to catch in a lagoon. Yes....

He lay still, surveying other aspects of the situation. Davis had called on an aircraft carrier for electronic items, and the Esperance was in constant touch with somebody by short-wave radio. It might be the same carrier. The Manila police department was on very cordial terms with Davis, and the staff of a satellite-tracking installation saved odd specimens of fish for him.

The Esperance's enterprise was plainly not a brand-new adventure. It had been carried on for some time. They had had technical aid of the very highest caliber, but they hadn't gotten anywhere yet. It did appear that Terry had added a minor specialty to the arsenal of investigative techniques. Without the data gathered on recorder-tape, their idea of the events of two nights before would be very different. The sea would have seemed very bright, then the glowing area would have been noted to have grown smaller, and something resembling a whale would have been seen leaping high above the water. Then the brightness would have faded out. It would have been mysterious enough, but an entire aspect of the phenomenon would have gone unnoticed. There was still no answer to any of the far-reaching questions Terry had asked himself, but most of them had never been asked before. Sea noises had proved to be closely connected to whatever had to be found out. What was known about them was due to his findings. He'd established a new frame of reference.

And he'd discovered the solution of a minor problem before the problem was even stated. He had only to prove it. Then, of course, there would be other problems arising from it.

He got up, put on swimming trunks, and duck trousers over them. He slipped into a sweat shirt and went upon deck. Deirdre hailed him.

"Good morning! Everybody's over at the tracking station, arguing about the bolide that went over last night. According to the radar, it plunged into the sea, miles and miles away."

"What should it have done?" asked Terry. "I'm not familiar with meteorites. Are they planning to dive for it?"

"Hardly!" Deirdre laughed. "It landed in the Luzon Deep." She waved a hand in an inclusive gesture. "This island's on the brink of it. A bathyscaphe might go down there—in fact, I think it's scheduled; you know, the one I said was coming to Manila on the oceanographic ship? A bathyscaphe can go that deep, but it's not likely to hunt for meteorites."

"Ah," said Terry judicially. "Then what difference does it make where it hit?"

"It didn't fall the way it should have," said Deirdre. "It was spotted by space radar away out, and they tried to compute its path, but they figured it wrong. Now they're trying to make it come out right by allowing for the effect of the earth's magnetic field on a metal meteorite. They're arguing and waving equations at each other."

"Let them," said Terry. "I have trouble enough with fish. Do you think I could borrow a boat?"

"We've always been able to," said Deirdre. Then she added, "I've kept your breakfast hot. While you eat it I'll get a boat."

She went below, and instants later was up again.

"I have a feeling," she said, "that something interesting is going to happen. I'll be back."

She swung lightly to the wharf and headed for land. Terry went below, to find his breakfast laid out on the cabin table. He settled down to it, but first pulled a book from the shelves. It was a volume on oceanography, and its pages showed that it had often been referred to. He found the Luzon Deep described. Its area was relatively small, a mere ninety-mile-long chasm in the sea-bed. But it was second only to the Mindanao Deep in its soundings, and a close second at that. Its maximum depth was measured at twenty-seven thousand feet. Over five miles. There was a mention of Thrawn Island as being on the very edge of the Deep. According to the book, the island was the peak of one of the most precipitous and tallest submarine mountains in the world. Three miles from where Thrawn Island lay, there were soundings of twenty-eight thousand feet and upward. This depth extended as a trench....

The staccato roaring of an outboard motor sounded some distance away. It bellowed toward the yacht, swung about, and cut off. Terry gulped down his coffee and went abovedecks, just as Deirdre was fastening the small craft alongside the yacht.

"Taxi?" she asked amiably. "I got the boat. Where to?"

Terry swung down and took the steering grip. He headed the boat away. There was a box for bait, a few fishing lines, and even two highly professional fish-spears on board. Fishing was not necessarily a sedentary pastime here.

"We try the lagoon entrance," he said. "I've an idea. I noticed something last night, when we came in."

"Do you want to brief me?"

"I'd rather not," he admitted.

Deirdre shrugged without resentment. The little craft went sturdily toward the passageway to the open sea. She formed an arrowhead of waves as she moved. She neared the points of land at the ends of the coral formation enclosing the lagoon. Thrawn Island was not an atoll. But the beaches were made of snow-white coral sand. Outside there was clear water for a space and then a reef on which the seas broke.

Terry headed the boat toward the open sea. Almost immediately after, there was nothing but the reef and the sea between the boat and the horizon. He slowed the boat almost to a stop, well within the reef's tumult. She swayed and rolled on the surging water.

"Stay here," he commanded. "I want to swim out and back."

He pulled the sweat shirt over his head. He jumped overboard, leaving Deirdre in charge of the boat.

The world looked strange to him when waves rolled by higher than his head. A few times the sky narrowed to the space between wave-crests. Other times he was lifted upon a wave-peak, and the sky was illimitably high and large, and the breaking seas on the nearby reef merely roared and grumbled to themselves.

He swam out, away from the land. Suddenly his body began to tingle. He stopped and paddled, analyzing the sensation. One side of his body felt as if the most minute of electric currents entered his skin. It was not an unpleasant sensation. Deirdre, in the small boat, was fifty yards behind, watching him. As he swam on, the tingling grew stronger. He dived. The tingling did not vary with depth. He came up, and he was farther out than he'd realized.

He suddenly knew that he'd been incautious. There are currents which flow in and out of lagoons. A barrier of reef affects them, too. Terry found himself swimming in an outward-bound current, which pushed him out and away from the island.

Within seconds the sensation in his body changed from a mere tingling to torment. For a moment it was just very much stronger and slightly painful, but a moment later it felt as if he swam among flames. It was unbearable. His muscles were not contracted, as if by an electric shock, but he couldn't control their reflexes. He found himself splashing crazily, trying to fight his way out of the anguish which engulfed him.

He went under. His body had taken complete control over his mind, and he found himself swimming frantically, underwater. He couldn't reach the surface. His body tried to escape the intolerable agony in which it was immersed but couldn't.

He heard a roaring sound, but it meant nothing. The roaring grew louder. Finally, he did break surface for a few seconds, and he gasped horribly, but then he went under. The roaring grew thunderous, and he broke surface again....

Something seized his flailing arm and pulled him up. The arm ceased to experience the horrible sensation of being in boiling oil. His hand recognized a gunwale. He swarmed up the solid object with hands helping him, and found himself in the boat, gasping and shivering, and cringing at the bare memory of the suffering he'd undergone.

Deirdre stared at him, frightened. She swung the boat's bow shoreward. The outboard motor roared, and the boat raced past the gap in the reef and rushed toward the lagoon opening.

"Are you all right? What happened? You were swimming and suddenly...."

He swallowed. His hands quivered. He shook his head and then said unsteadily, "I meant to ... check the reason those queer fish stay in the lagoon. I thought that if they belonged in the depths and were somehow carried out of them, they would try to get back. I found out!"

He felt an unreasonable relief when the lagoon entrance was behind the boat. The glassy water was reassuring. The Esperance looked like safety itself.

"I think I know how they got here, now," he added. "We underestimated what we're trying to understand. I'll be all right in a minute."

It was less than a minute before he shook himself and managed to grin wryly at Deirdre.

"Was there a hum in the water?" asked Deirdre, still staring at him. "I thought I heard it on the bottom of the boat. Was that the trouble?"

"Yes. I wouldn't call it a hum," Terry admitted. "Not any longer. Now I know what a slow fire feels like."

"You frightened me," said Deirdre, "the way you splashed...."

"I heard the humming sound," said Terry, "last night when the yacht came up to the island. We were perhaps a half-mile off-shore. It was very faint, but I had the amplifier turned down low. The hum was at its loudest just before we passed the reef, but nobody else noticed. When Dr. Morton said there were abyssal fish in the lagoon, I knew why they'd be there. I made a guess at what might drive them there. I went to find out if I was right. I found out!"

"The hum?" asked Deirdre again. When he nodded, she said: "What are you going to do now? What do you think makes the hum?"

"I'm trying hard not to guess what makes the hum," Terry told her. "Insufficient data. I need more. I think I'll ask what other odd phenomena have turned up in this neighborhood. Foam-patches on the sea? I can't imagine a connection, but still...."

He swung the little boat alongside the docked Esperance and held out his hand to help Deirdre to the dock. His hand was wholly steady again. She accepted the help.

"We'll go to the tracking station?"

"Yes. Everybody seems to be there," said Terry.

They heard a babble of voices coming from the satellite-tracking station. As they approached the buildings, Terry looked around. Off at one side there was the very peculiar aerial system by which tiny artificial moons circling the earth could be detected by their own signals. Minute spheres and cylinders and spiky objects and foolish-looking paddle-wheels, whirling in their man-appointed rounds, sent down signals with powers of mere fractions of a watt. This system of aerials picked up those miniature broadcasts and extracted remarkable amounts of information from them. It was possible to determine the satellites' distance more accurately, by a comparison of phase-changes in their signals, than if steel tape measures were stretched up to make physical contact with them. The accuracy was of the order of inches at hundreds of miles. Floating where the stars were bright and unwinking lights against blackness and the sun was a disk with writhing arms of fire, the small objects sent back information that men had never possessed before and did not wholly know what to do with now that they did. And there were other objects in the heavens, too. There were satellites which no longer signaled back to earth. Some had their equipment worn out. Some objects were satellites which had failed to function from the beginning. Some were mysteries.

The bolide of the night before was a mystery. As Terry and Deirdre entered the wide verandah of the recreation building for the station's personnel, they heard Dr. Morton protesting, "But that's out of the question! I agree that we never know any more about what the Russians throw out to space than what we find out for ourselves. That's true! But this wasn't a terrestrial object! If it was a satellite that wasn't launched right, it had to be sent up from Russian territory. It wasn't. That's positive! If we assume it was a satellite that had already made several orbital turns, we must admit it would be an impossible shift in apogee for it to come down at the angle it did!"

Deirdre and Terry sat down as someone else said hotly, "Our observations were wrong. They had to be! The earth's magnetic field couldn't affect the speed of an object outside the atmosphere! Our observations say it slowed down. It couldn't!"

Davis lifted a hand in greeting. The argument stopped for a moment. Deirdre was known, but Terry had to be introduced. He was sitting beside a bald young man who explained in a low tone, as the argument resumed. "They're having fun. They argued for days when our radar picked up an empty second stage in orbit. They're still ready to dispute for hours about a supposed retrograde satellite that was spotted last year, was watched for four turns, and then disappeared. Beer?"

"Too early," said Terry. "Thanks just the same."

Davis said earnestly, at the other side of the room, "I'd feel a lot better if that thing last night hadn't splashed where it did."

"The bolide," said a voice humorously, "is a free animal."

The discussion went on. Terry saw Deirdre talking to a middle-aged woman with a splendid sun-tan and a placid expression on her face. Doug and Tony sat watchfully on the side lines, listening. Doug had been offered, and had accepted, a sandwich. He ate it methodically.

Terry had a sudden feeling of unreality. Less than half an hour before he'd been in torment and, but for Deirdre, on his way to death. On the Esperance there'd been so much that was absorbing in the way of fish behavior that he'd forgotten some people were interested in other things. Here a dozen people squabbled over the behavior of a meteorite. Nothing could be of less consequence to the outside world. But in the outside world, people argued about baseball, or golf, or politics....

Doug excused himself and slipped outside. Terry joined him there a little later. Doug was smoking a cigarette, looking at the sky and the palms.

"Pretty heavy discussion," said Terry.

"It's over my head," said Doug. "I got lonesome. It made me think of my girl. She likes to talk like this. That's why ..."

He stopped.

"Is there an aqualung outfit on the Esperance?" asked Terry.

"Sure! Two or three of them. Mr. Davis had an idea they'd be useful. Used one of them last week to look at the Esperance's bottom-planks. Why?"

"I'd like to poke around the bottom of the lagoon a little," said Terry, with unconscious grimness. "Would you help?"

"Sure!" said Doug.

They went back to the Esperance. Doug got out two aqualung outfits. They checked the valves and tanks and connections. Doug brought out two spring guns. In half an hour they were in the outboard, headed for what Doug said was the deepest part of the lagoon.

Arrived there, Terry tested the water with his finger and then went overside. Instead of a spring gun, he used one of the fish spears that seemed to be standard equipment for fishing, here. Doug stayed in the boat to watch.

Terry'd guessed that what he looked for would be in the deepest part of the lagoon. He was right. Within half an hour he'd speared five fish of types that had no business being within two thousand fathoms of the surface. He ignored the lagoon's normal inhabitants. He picked on fish of a dark-red color, which is predominant in the depths but not elsewhere. When the fish had extremely small eyes or extremely large ones, he hunted them determinedly, knowing they were deep-sea fish. He caught five, which was a good haul, even considering his previous suspicions.

Doug inspected the catch as the outboard went back to the yacht. Terry replaced his spear under the gunwale.

"They're queer fish," observed Doug. "I wouldn't want to eat them."

"Neither would I," agreed Terry. "But I feel a certain sympathy for them. I think we've shared an experience."

He did. Fish so far from their normal environment would not have migrated unless they'd been forced to. So these fish must have been driven up from the blissful utter blackness of the abyss, which was their habitat. He had a vivid memory of the kind of urging they'd received, because of his recent swim outside the reef opening. That was the experience he believed they shared.

He got his catch onto the Esperance's deck and found some sharp knives in the galley, while Doug put the aqualungs away. When Doug came abovedecks again, he looked distastefully at the work Terry had undertaken.

"Do you like to do that sort of thing?" he asked.

"Hardly!" said Terry. "But I want to get it done."

Doug watched for a moment or two.

"I'm pretty keen about poetry. Sometimes I feel I've got to sweat over a poem that I need to get written. It's hard work. There's no real sense to it. But I feel it's got to be done. I guess that's the way you feel now."

"Perhaps," said Terry.

It wouldn't have occurred to him to liken the writing of verses to the dissection of dead deep-sea fish, but Doug had a point. He went away presently, and Terry completed the highly unpleasant task. He had just finished flushing the deck clean when Deirdre came back from the tracking station. He was already at work on the recorder when she stepped onto the deck.

"You didn't stay," said Deirdre. "I was waiting for a chance to tell my father about the hum outside the lagoon, but he was as deep in the meteor argument as any of them. I still haven't told him."

"There's something else to tell him now," Terry remarked. "I went down with an aqualung. Doug was standing by," he added at her gesture of protest, "and speared some fish that don't belong here. I've dissected them. Their swim bladders had been very skillfully punctured, so if they went or were driven into lesser pressure, they'd leak instead of bursting. That's how they survived coming up from the depths. But the main thing is this."

He held out a small plastic object in his hand. It was about an inch in diameter and two in length, and there were inclusions in the clear material. There were plates and threads of metal. They had that look of mysterious purpose that highly-developed technical devices have.

"This was fastened to the fin of a fish that belongs as far down as a fish can go," he said. "I've found out one of its purposes. When it is in the water, it makes a sound more acute than a whistle every time another sound strikes it. Try that on your piano!"

Deirdre stared.

"I'm saying," he repeated, "that it takes in one sound and gives out another. It's ... it could be a relay. What is that for? What's it all about? What does it mean? And I ask just those questions because I don't dare ask who and why!"

"What ... what will you do?" asked Deirdre absurdly.

"I've no idea," Terry told her. "I've got a feeling that the wise thing to do would be to settle down somewhere and buy a shop, and forget all this. If I don't think about it, maybe it'll go away."

"I'll get my father and see what he says."

"Tell him," commanded Terry, "that I want to try out my fish-driving horn. I'd like to have witnesses. If this foolishness has to be reported to somebody, we need evidence of the facts. I want to drive fish and see how many deep-sea ones there are in this lagoon, and how many of them have spy-devices on them."

Deirdre turned away. Then she turned back.

"Spy-dev—"

"I slipped," said Terry. "I shouldn't have said that. Forget it. Just tell your father I have an extremely urgent impulse to drive fish, and would he come and help."

Deirdre looked at him strangely, and went onto the wharf to search for her father.

Terry paced back and forth on the Esperance's deck. In a few minutes Davis and the crew-cuts appeared with Deirdre. But they were not alone. Straggling behind them came nearly all the personnel of the tracking station. There would be somebody on official duty, of course. But here was the bespectacled Dr. Morton; the bald young man who'd offered Terry beer; and the installation cook; a typist, and specialists in radar and other abstruse subjects.

Deirdre said, "I told them about the fish-driving business and they want to see. They stopped arguing about last night's bolide to take ringside seats. All right?"

Terry shrugged. He had the recorder already set up. He'd taken a section of the tape made where the sea was bright, at the place where the loudest of the unpleasant humming noise was recorded. He'd made a loop of it so it would play over and over.

He played the much-amplified sound through the underwater horn held in the air. The result was a raucous bellowing noise. He lowered it into the water. The horn touched the surface and went under.

Instantly, the fish of the lagoon seemed to go crazy. All the surface broke and writhed and splashed. There was an incredible number of fish. Terry turned the horn on one side. In this way, not all the water was filled with the intolerable noise, but only a net-like beam of it raced across the water. Within that line the fish continued to leap frenziedly. The rest of the lagoon suddenly quieted down. In a little while the beam's space, also, grew quiet. But that was because the fish that had been previously caught in it had escaped.

"I'm afraid," said Terry, "that this isn't going to be very entertaining. I'm going to sweep the beam across the lagoon, pushing the fish ahead of it, until I should have them all in one small area."

It was curious that he felt uncomfortable as he set about his task. But he'd experienced the sensation this sound produced. And it was not very pleasant.

He turned the beam around, slightly. Again, there were sudden splashings. They died away. He turned the beam again. It was a nasty, snarling vibration in the water. So far as fish were concerned, it was more like a wall than a net, because not even the tiniest living creature could penetrate it. Not only fish fled before it. Shrimps and crabs and all types of crustaceans jerked and crawled and swam ahead of its motion. Jellyfish writhed when it touched them. Sea cucumbers contorted themselves. Everything that lived in the lagoon and could swim or crawl or writhe moved before the invisible barrier. Presently, the effect of crowding could be seen, and fish began to leap out of water.

"This is a great advance in civilization," said Dr. Morton. "Men invented guns and destroyed the buffalo and the passenger pigeon! You may have made it possible to depopulate the sea!"

Terry did not answer. The morning sun shone brightly, a gentle breeze made ripplings on the lagoon, the palms waved their fronds in languid gestures, and the surf could be heard booming and splashing on the outer reef. And about two dozen people stood on the wharf or on the Esperance's deck and watched a spliced section of recorder-tape go through and through a recorder, which was set to make a sound underwater that could not be heard by the people above.

The fish of the lagoon had crowded themselves into a minor embayment of the shore. There were innumerable leapings there.

"There should be plenty of fish collected now," said Terry distastefully. "I certainly can't herd them ashore."

The outboard boat pushed away from the yacht, its motor roaring. It reached the area in which the water seemed to seethe and surge with the motion of densely-crowded swimming creatures. The people in the boat examined the surrounding water, then the boat came back at top speed.

"They're there!" called Davis. "And thick enough to walk on! I clearly saw some freaks that must come up from the bottom! We want to collect them!"

"I speared five just now," Terry told him, "and one of them was wearing this."

He held up the plastic object he'd found. There was silence for a moment. Then Dr. Morton said briskly, "We'll want fish spears. We'll take all the boats and go after some more of these piscatory oddities. Who's best with a spear?"

Davis would go. He could use the two fish spears that were standard equipment for the outboard. The staff of the tracking station scattered to launch other boats. Only Terry and Deirdre remained on the Esperance. It was necessary for someone to stand by the recorder.

Boats moved away across the water. One stout member of the island's staff trudged along the shore.

"You're driving them," said Deirdre. "You are right."

"I wish I weren't," said Terry.

"Why?"

"You know how these weird fish got here," he said impatiently. "They were driven here. You know how they've been kept here. I experienced that! I told you why they didn't die when they came up from thousands of fathoms! Now, what's the only possible purpose for their being here? Put it more scientifically! What is the consequence of these happenings, so that to some biological entity it would be a favorable happening?" His tone was sardonic, at the end.

"I don't know."

"I hope I don't either," said Terry dourly.

He was in no amiable mood. He'd made too many guesses like those Davis had mentioned. He was beginning to have less and less hope that they were untrue. Each new development made any imaginable cause of these events just so much more appalling to think about.

In an hour, three boats came back from the small bay into which all the fish of the lagoon had been crowded. Terry turned off the underwater horn. A stout man walked slowly along the shore with a heavy burden of known edible fish. He was the island's cook, and he had speared them from the beach. The boats, altogether, had speared and captured not less than sixty specimens of fish normally found only many thousand feet below the ocean's surface. Upon inspection, all of them were found to have deftly punctured swim bladders, punctured with so slender a barb that the opening would close by itself, except when serving for the release of intolerably expanding gas.

Before noon, seven more plastic objects had been found among the deep-sea fish. Three seemed identical to the one Terry had found. Two others were identical to each other but of a different kind, and the last two were of two different types altogether. Only those like the one tested by Terry seemed sensitive to sounds, which they changed into other sounds at a twenty-thousand-cycle frequency, or higher. The rest did nothing that could be detected.

During the afternoon, news came to distract the absorption of the tracking station staff in the lagoon's fish. The short-wave operator came running to the wharf, waving a written message. The deck of the Esperance was not a pretty sight, just then, with the dissection that had been taking place on it. Jug was beginning to flush the debris overside.

The short-wave operator arrived. Dr. Morton read the message. He raised his voice.

"Here's a fancy one!" he told the assembled company. "Space-radar's picked up a new object coming in from nowhere. It will probably orbit once before it hits the air and burns. By the line of motion it should pass nearly overhead here. We're alerted to get it under observation and watch it!" He waved the message in a large gesture. "We've got to get ourselves set up! The argument on the path of last night's bolide and why it fell where it did is again in order. We'll see what we can do about computing the fall-point of this!"

He headed for the shore. The staff followed, babbling. Somebody's mathematics would be verified, and with it his views on the possible effects of terrestrial magnetism on objects approaching the earth.

"We ought to get these plastic things to Manila," Davis said slowly. "They need to be compared to others. But I think we'll wait and see this bolide first."

A heated argument started in the tracking station staff. From Dr. Morton downward, almost to the station's cook, the most varied predictions were made. The official computation from Washington, made from the observed course and height and speed, predicted that the bolide would land somewhere in the South Pacific. Dr. Morton predicted a fall in the China Sea, within a certain precisely stated number of miles from Thrawn Island. Other predictions varied.

At exactly fourteen minutes after eight—a time way ahead of the official schedule but exactly as Dr. Morton had predicted—the bolide passed overhead. It was an amazing spectacle. It left a trail of flame behind, across thirty degrees of sky. It went on and on....

Less than ten minutes later the short-wave radio informed the island that the shooting star had been seen to fall in the sea. It had been observed by a plane which was then circling over the area in which the Esperance had encountered the circle of shining sea. The plane was there to see if the phenomenon would occur again. It didn't.

But the plane saw the bolide as it struck the sea, and huge masses of steam and spray arose. The bolide was not white-hot, then, as when it passed over Thrawn Island. It was barely of dull-red brightness. It hit the sea and sank, leaving steam behind.

The water was forty-five hundred fathoms deep at that point.

---