Ramsey frowned at his snifter. The signal remained stationary although Bonnett was moving. But then a signal device could have been left hidden forward. He moved the snifter to the right, aiming it toward the center of the dive board. The signal remained constant.

Sparrow had followed the motion.

"It's in the board!" shouted Ramsey.

Sparrow whirled toward the board. "We may have only a couple of minutes to get that thing!"

For a mind-chilling instant, Ramsey visioned the enemy wolf packs converging for another kill -twenty-one.

Garcia slammed a tool kit onto the deck at their feet, flipped it open, came out with a screw driver. He began dismantling the cover plate.

Bonnett entered. "What's wrong, Skipper?"

"Spy-beam transmitter," said Sparrow. He had found another screw driver, was helping Garcia remove the cover plate.

"Should we take evasive action?" asked Ramsey.

Sparrow shook his head. "No, let them think we don't know about it. Steady as she goes."

"Here," said Garcia. "Pull on that end."

Ramsey reached forward, helped pull the cover plate away from the board, revealing a maze of wiring, transistors, high-pressure tubes.

Bonnett picked up the snifter, passed it in front of the board, stiffened as the signal increased in front of the tube bank.

"Joe, stand by on the auxiliary dive board," said Sparrow. "I'm shutting down this whole section."

Garcia darted across to the auxiliary board on the opposite side of the control room. "Auxiliary operating," he called.

"Wait," said Bonnett. He held the search box steady before a tube, reached in with his free hand and pulled the tube from its socket. The signal continued, but now it emanated from Bonnett's hand as he waved the tube in front of the snifter.

"A self-contained power unit in that little thing!" gasped Ramsey.

"Suffering Jesus save us," muttered Sparrow. "Here, give it to me." He took the tube from Bonnett's hand, gritted his teeth at the heat of the thing.

Bonnett shook the hand which had held the tube. "Burned me," he said.

"It was in the ZO2R bank," Ramsey said.

"Smash it," said Garcia.

Sparrow shook his head. "No." He grinned mirthlessly. "We're going to gamble. Les, take us up to discharge depth."

"Six hundred feet?" asked Bonnett. "We'll be sitting ducks!"

"Do it!" barked Sparrow. He turned to Ramsey, extended the tube. "Anything special about this you could use to identify it?"

Ramsey took the tube, turned it over in his hand. He reached into his breast pocket, pulled out a tiny record camera, began photographing the tube from ail angles.

Sparrow noted the ready availability of a record camera, but before he could comment on it, Ramsey said, "I'll have to look at the enlargements." He glanced up at Sparrow. "Do we have time to give this thing a more thorough going over in the shack?"

Sparrow looked to the static pressure gauge. "About ten minutes. Whatever you do, don't stop that signal."

Ramsey whirled, hurried to the shack, Sparrow behind him. He heard Sparrow speaking into a chest mike as they ran.

"Joe, get a garbage disposal container and ready a tube to discharge that spy beam. With any luck at all, we're going to send the EPs chasing after an ocean current."

Ramsey put a piece of soft felt on his workbench, placed the tube on it.

"If you've ever prayed, pray now," said Sparrow.

"Nothing this small could have an internal power source to give off that much signal," said Ramsey.

"But it does," said Sparrow.

Ramsey paused to wipe perspiration from his hands. A thought flitted through his mind: What will the telemeter record show on Sparrow's endocrine balance this time?

"Devilish thing!" muttered Sparrow.

"We're playing a big gamble," said Ramsey. He placed calipers over the tube, noted the measurements. "Standard size for the ZO2R." He put the tube in a balance scale with another of the same make. The spy tube sank, unbalancing the scale.

"It's heavier than the standard," said Sparrow.

Ramsey moved the balance weights. "Four ounces."

Bonnett's voice came over the bulkhead speaker above their heads: "Estimating discharge depth in four minutes. We've picked up a free ride on a cut rent."

Sparrow said, "Do you think you can find out any thing else about that thing?"

"Not without tearing it down," said Ramsey. "Of course, there's a possibility X-ray would show some internal detail we could figure out." He shook his head.

"There'll be more of those aboard," said Sparrow. I know there will."

"How?"

Sparrow looked at him. "Call it a hunch. This mission has been marked." He glared at the tube on the bench. "But by all that's sacred, we're going to come through!"

"Two minutes," said Bonnett's voice over the speaker.

Ramsey said, "That's it. Let me examine what we already have."

Sparrow scooped up the tube, said, "Move out to full limit."

"They may detect our pulse," said Ramsey, then colored as he felt the metronomic response of the speaker in his neck.

Sparrow smiled without mirth, turned, stooped for the door, and disappeared down the companionway. Presently, his voice came over the intercom: "We're at the tube and ready to blow this thing, Les. Give me the static gauge readings."

Back came Bonnett's voice: "Four-ninety, four-seventy, four-forty . . . four hundred even!"

Ramsey heard the fault "chug!" of the discharge tube, the sound carried to him through the hull.

Sparrow's voice rang over the intercom: "Ride the vents!"

The Ram's deck tipped sharply. The humming of the motors climbed through a teeth-grating vibration.

Ramsey looked to the dial showing their sound-transmission level. Too high. The silencer planes would never cover it.

Sparrow's voice boomed from the speaker: "Ramsey, take over the internal-pressure system on manual. Overcompensate for anticipated depth. We'll worry about Haldane charts and depth sickness later. Right now, I want that cold level and 7000 feet over us."

Ramsey acknowledged, his hands moving to the controls as he spoke. He glanced at the vampire gauge on his wrist. Diffusion rate low. He stepped up the release of carbonic anhydrase into the atmosphere.

Sparrow again: "Ramsey, we've fired a salvo of homing torps on our back path. Delayed timing. Track the signal if any of them blow."

"Aye, Skipper." Ramsey plugged a monitor phone into one of the board circuits ahead of him, glanced to the telltale above it. As he did, he noted that the pellet in his neck had almost lost the sound of the tube behind them. His hands continued to move the internal pressure ahead of the depth requirement. The outside pressure repeater above his head showed 2600 pounds to the square inch, still climbing. Abruptly, the temperature recorder responded to their entrance into the cold current.

Ramsey spoke into his chest mike: "We're in the cold, Skipper."

Back came Sparrow's voice: "We have it here." Ramsey's pressure repeater climbed through 2815 pounds, steadied. He felt the deck beneath him come up to level. Relays clicked, a bank of monitor lights flashed green. He sensed the ship around him -- a buoyant, almost living thing of machines, plastics, gases, fluids . . . and humans. He could hear Sparrow's voice over the open intercom giving orders in the control room.

"Force speed. Change course to fifty-nine degrees, thirty minutes."

The secondary sonoran chart at Ramsey's left noted the course change. He looked at the red dot marking their position: almost due south of the western tip of Iceland, directly on the sixtieth parallel of latitude. Automatic timelog reading: seven days, fourteen hours, twenty-six minutes from start of mission.

"Ramsey, anything on those fish we sent back?"

"Negative, Skipper."

"Stick with the shack. We're going to start tearing down the board. We'll have to check every tube for deviation from standard weight."

"We'll have to go over the shack and the E-stores, too," said Ramsey.

"Later." Sparrow's voice conveyed a calm surety.

Ramsey glanced at his wrist watch, correlated it with the timelog. What will the telemeter show? he asked himself. Again, he felt that his mind had made a failing grasp at an elusive piece of essential knowledge. Something about Sparrow. Ramsey's gaze ranged over the board in front of him. His ears felt tuned for the slightest sound over the monitor phones. He glanced at the oscilloscope in the right bank: only background noise. For a fleeting instant, Ramsey felt that he was one with the ship, that the instruments around him were but extensions of his senses. Then it was gone and he could not recapture the feeling.

In the control room, Sparrow fought down the twitching of a cheek muscle. He replaced a tube in the sonoran system, extracted another, read the code designation from the tube's side: "PY4X4."

Garcia, beside him, ran a finger down a check list: "Fifteen ounces plus."

Sparrow checked it on a balance scale. "Right on." He replaced the tube, said, "You know, when I was in high school they were saying that someday they'd run systems like this with transistors and printed circuits."

"They did for a while," said Garcia.

"Then we got into sweep circuits," said Sparrow. He pulled out an octode cumulator tube, read off the code, checked the weight.

"We could still get by with Lighter stuff if it weren't for high atmospheric pressures." He went on to another tube. "What we need is a dielectric as tough as plasteel."

"Or an armistice," said Garcia. "Then deep-tug equipment would be specialty stuff."

Sparrow nodded, pulled another tube from its socket.

"Skipper, what is that Ramsey?" asked Garcia.

Sparrow paused in the process of weighing a tube, looked at Garcia. "I think he's a Security man planted on us."

"That occurred to me," said Garcia. "But have you asked yourself yet who planted the spy beam on us? He could be a sleeper. He could be, Skipper."

Sparrow's hand trembled as he reached for another tube to weigh. He brought back his hand empty, wiped the palm on his shirt, looked down at Garcia. "Joe --" He broke off.

"Yes?"

"Has it ever occurred to you that humanity's basic problem is all wrapped up in the idea of Security?"

"That's a big mouthful, Skipper."

"I mean it, Joe. Look, I know what I am. I can even tell you what my conception of myself is. How you have nothing to fear from me. Les can do the same thing. And you. And Ramsey." He wet the comers of his mouth with his tongue, stared wide-eyed at Garcia. "And any one of us or all of us could be lying."

"That's not a Security problem, Skipper. That's a problem in communications. Ramsey's department."

Sparrow turned back to the board without answering, went on with his patient inspection.

"I'd like to know what that last-minute Security inspection of Ramsey was all about," said Garcia.

"Shut up!" barked Sparrow. "Until there's proof positive to the contrary, he's one of us. So are you and Les. And so am I." His mouth twisted in faint amusement. "We're all in the same boat." The lips thinned. "And we've a bigger and more immediate problem." He balanced a tube on the scales, replaced it. "How can we break radio silence to notify home base of what we've discovered?"

A distant dull thump pounded through the hull. A second one.

Ramsey's voice over the intercom: "Skipper! Two hits! Blast pattern identical to our fish!" His voice rose in pitch: "Breaking up noises! Two sources. Skipper! We got two!"

"God forgive us," said Sparrow. "God forgive us." More thudding sounds resonating through the hull, a strange double beat.

"Anti-torp seekers," said Ramsey. "They've knocked out the rest of our fish."

"Those men didn't stand a chance," said Sparrow. His voice lowered, became almost inaudible. "'He that smiteth a man, so that he die, shall be surely put to death. And if a man lie not in wait, but God deliver him into his hand; then I will appoint thee a place wither he shall flee. But if a man come presumptuously upon his neighbour, to slay with guile; thou shalt take him from mine altar, that he may die.'"

Across from him, Bonnett held up a tube. "Joe, what's standard on a GR5?"

Garcia glanced at Sparrow, who turned abruptly back to his examination of the board. "Eight ounces," said Garcia.

"That's what I make it," said Bonnett. "But this one tops thirteen." A tone of suppressed excitement vibrated in his voice.

Sparrow looked aft, lips trembling.

"I think I have one, Skipper," said Bonnett.

Garcia had stepped across to Bonnett's side. He took the tube from the first officer.

"There should be a better way to live and a better way to die," said Sparrow. He shuddered, stabbed a glance at Bonnett. "Well, set it aside and see if there are any more!"

Bonnett appeared about to reply, but remained silent. He reclaimed the tube from Garcia, deposited it gently in a padded tray of his tool box.