Reid cried out, "A message is coming through, Al."

"From the Proteus?" Carter ran to the window.

"Well, not from your wife."

Carter waved his hand impatiently. "Later. Later. Save all the jokes and we'll go over them one by one in a big heap. Okay?"

The word came through: "Sir, Proteus reports DANGEROUS AIR LOSS. REFUELING OPERATION CARRIED THROUGH SUCCESSFULLY."

"Refueling?" cried Carter.

Reid said, frowning, "I suppose they mean the lungs. They're at the lungs, after all, and that means cubic miles of air on their scale. But ..."

"But what?"

"They can't use that air. It's unminiaturized."

Carter looked at the colonel in, exasperation. He barked into the transmitter. "Repeat the last sentence of the message."

"REFUELING OPERATION CARRIED THROUGH SUCCESSFULLY."

"Is that last word `successfully'?"

"Yes, sir."

"Get in touch with them and confirm."

He said to Reid, "If they say `successfully,' I suppose they handled it."

Reid nodded his head. He looked up at the Time Recorder, which read 37, and said, "The pleural lining is a double membrane surrounding the lungs. They must be moving in the space between; a, clear road, an expressway really, right to the neck."

"And they'll be where they started half an hour ago," grated Carter. "Then what?"

"They can back into a capillary and find their way to the carotid artery again, which is time-consuming; or they may by-pass the arterial system by taking to the lymphatics, which involves other problems. -Michaels is the pilot; I suppose he'll know what to do."

"Can you advise him? For God's sake, don't rest on protocol."

Reid shook his head. "I'm not sure which course is wisest, and he's on the scene. He'll be a better judge as to how well the ship can withstand another arterial battering. We've got to leave it to them, general."

"I wish I knew what to do," said Carter. "By the Lord, I'd take the responsibility, if I knew enough to do so with a reasonable chance of success."

"But that's exactly how I feel," said Reid, "and why I'm declining the responsibility."

Michaels was looking over the charts, "All right, Owens, this wasn't the place I was heading for, but it will do. We're here and we've made an opening. Head for the crevice."

"Into the lungs? said Owens, in outrage.

"No, no." Michaels bounded from his seat in impatience and climbed the stairs so that his head poked into the bubble. "We'll get into the pleural lining. Get the ship going and I'll guide you."

Cora knelt at Grant's chair. "How did you manage?"

Grant said, "Barely. I've been scared more times than I can count-I'm a very scary person-but this time I nearly set a record for fright-intensity."

"Why do you always make yourself out to be such a coward? After all, your job ... "

"Because I'm an agent? Most of it is pretty routine, pretty safe, pretty dull; and I try to keep it that way. When I can't avoid frightening situations, I have to endure them for the sake of what I believe I'm doing. I'm sufficiently brainwashed, you know, to think it the patriotic thing-in a way."

"In a way?"

"In my way. It's not just this country or that, after all. We're long past the stage where there can be a meaningful division of humanity. I honestly believe our policies are intended to uphold the peace and I want to be part, however small, of that upholding. I didn't volunteer for this mission, but now that I'm here ..." He shrugged.

Cora said, "You sound as though you're embarrassed to be talking about peace and patriotism."

Grant said, "I suppose I am. The rest of you are driven by specific motivation, not by vague words. Owens is testing his ship; Michaels is piloting a course across a human body; Duval is admiring God's handiwork; and you..."

"Yes?"

Grant said softly, "You are admiring Duval."

Cora flushed. "He's worth admiration, he really is. You know, after he suggested we shine the ship's headlights into the crevice so as to give you something to shoot for, he did nothing further. He wouldn't say a word to you on your return. It's his way. He'll save someone's life, then be casually rude to him and what will be remembered will be his rudeness and not his life-saving. But his manner doesn't alter what he is."

"No. That's true; though it may mask it."

"And your manner doesn't affect what you are. You affect a brittle, adolescent humor in order to mask a deep involvement in humanity."

It was Grant's turn to redden. "You make me sound an uncommon jackass."

"To yourself perhaps. In any case, you're not a coward. But now I've got to get to work on the laser." She cast a quick glance at Michaels, who was returning to his seat.

"The laser? Good Lord, I'd forgotten. Well, then, do your best to see it's not crucially damaged, will you?"

The animation that had brightened her through the previous conversation died away. "Oh, if I only could."

She moved to the rear

Michaels' eyes followed her. "What about the laser?" he said.

Grant shook his head. "She's going to check now."

Michaels seemed to hesitate before his next remark. He shook his head slightly. Grant watched him but said nothing.

Michaels settled himself into his seat and said at last, "What do you think of our present situation?"

Grant, until now absorbed in Cora, looked up at the windows. They seemed to be moving between two parallel walls that almost touched the Proteus on either side; gleaming yellow and constructed of parallel fibers, like huge tree trunks bound side by side.

The fluid about them was clear, free of cells and objects, almost free of debris. It seemed to be in dead calm and the Proteus churned through it at an even, rapid clip with only the muffled Brownian motion to interject any unevenness into its progress.

"The Brownian motion," said Grant, "is rougher now."

"The fluid here is less viscous than the blood plasma so the motion is less damped out. We won't be here long, however."

"We're not in the blood-stream, I take it, then."

"Does it look like it? This is the space between the folds of the pleural membrane that lines the lungs. The membrane on that side is fixed to the ribs. In fact, we ought to be able to see a huge gentle bulge when we pass one of them. The other membrane is fixed to the lungs. If you want the names, they are the parietal pleura and the pulmonary pleura, respectively."

"I don't really want the names."

"I didn't really think you did. What we're in now is a film of lubricating moisture between the pleura. When the lungs expand during inhalation or contact during exhalation, they move against the ribs and this fluid cushions and smooths the motion. There's so thin a film that the folds of the pleura are commonly considered in contact in the healthy body, but being, germ-size we can sneak between the folds through the film of fluid."

"When the lung wall moves along the rib-cage, doesn't that affect us?"

"We are alternately hurried along slightly and held back slightly. Not enough to matter."

"Hey," said Grant. "Have these membranes anything to do with pleurisy?"

"They surely do. When the pleura are infected and inflamed, every breath becomes an agony, and coughing ..: '

"What happens if Benes coughs?"

Michaels shrugged. "In our position now, I suppose it would be fatal. We'd come apart. There's no reason for coughing, however. He's under hypothermia and in deep sedation and his pleura-take my word for it-is in good condition."

"But if we irritate them ..: '

"We're too small to do that."

"Are you sure?"

"We can speak only in terms of probabilities. The probability of a cough now is too small to worry about." His face was quite calm.

"I see," said Grant, and looked back to see what Cora was doing.

She and Duval were in the work-room; both heads bent closely over the bench.

Grant rose and went to the doorway. Michaels joined him.

On a section of opal glass, illuminated from below into bright milkiness, the laser lay disassembled, each part etched sharp and clear against the light.

"What are the total damages now?" demanded Duval, crisply.

"Just those items, doctor, and this broken trigger-wire. That's all."

Thoughtfully, Duval seemed to be counting the parts, touching each with a delicate finger and moving it. "The key to the situation then is this smashed transistor. What it amounts to is that there's no way now to fire the lamp, and that's the end of the laser."

Grant interrupted. "Are there no spare parts?"

Cora looked up. Her glance drifted guiltily away from Grant's firm eyes. She said, "Not anything built into the chassis. We should have brought a second laser but who could have ... If it hadn't come loose ... "

Michaels said, somberly, "Are you serious, Dr. Duval? Is the laser unusable?"

A note of impatience crept into Duval's voice. "I'm always serious. Now don't bother me." He seemed lost in thought.

Michaels shrugged. "That's it, then. We've gone through the heart, and we've filled our air chambers at the lungs, and all for nothing. We can't go on."

"Why not?" demanded Grant.

"Of course, we can go on as a matter of physical ability. It's just that there's no point in it, Grant. Without a laser, there's nothing we can do."

Grant said, "Dr. Duval, is there any way of performing the operation without the laser?"

"I'm thinking," snapped Duval.

"Then share your thoughts," snapped back Grant.

Duval looked up. "No, there's no way of performing the operation without the laser."

"But operations were performed for centuries without a laser. You cut through the lung wall with your knife; that was an operation. Can't you cut away the clot with your knife?"

"Of course I can, but not without damaging the nerve and placing an entire lobe of the brain in danger. The laser is incredibly more delicate than the knife. In this particular case, a knife would be butchery compared with a laser."

"But you can save Benes' life with the knife, can't you?"

"I think so, just maybe. I can't necessarily save his mind, however. In fact, I should think it almost certain that an operation with a knife would bring Benes through with serious mental deficiencies. Is that what you want?"

Grant rubbed his chin. "I'll tell you. We're heading for that clot. When we get there, if all we've got is a knife, you'll use a knife, Duval. If we lose our knives, you'll use your teeth, Duval. If you don't, I will. We may fail, but we won't quit. Meanwhile, let's look at it ..."

He pushed between Duval and Cora and picked up the 'transistor which lay neatly on the tip of his first finger. "Is this the broken one?"

"Yes," said Cora.

"If this were fixed or replaced, could you make the laser operate?"

"Yes, but there's no way of fixing it."

"Suppose you had another transistor about this size and power output and a thin enough wire. Could you piece it together?"

"I don't think I could. It requires such absolute precision."

"Perhaps you couldn't, but what about you, Dr. Duval? Your surgeon's fingers might be able to do it despite the Brownian motion."

"I could try, with Miss Peterson's help. But we don't have the parts."

Grant said, "Yes, we do. I can supply them." He seized a heavy metal screw-driver and moved purposefully back into the front compartment. He went to his wireless and without hesitation began to unscrew the panel.

Michaels moved behind him, seizing his elbow. "What are you doing, Grant?"

Grant shook himself free, "I'm getting at its guts."

"You mean you're going to dismantle the wireless."

"I need a transistor and a wire."

"But we'll be out of communication with the outside."

"So?"

"When the time come to take us out of Benes . . . Grant, listen ..."

Grant said, impatiently, "No. They can follow us through our radioactivity. The wireless is just for idle talk and we can do without. We have to, in fact. It's either radio silence or Benes' death."

"Well then, you'd better call Carter and put it to him."

Grant thought briefly. "I'll call him. But only to tell him there'll be no further messages."

"If he orders you to make ready for withdrawal."

"I'll refuse."

"But if he orders you ..:'

"He can withdraw us by force, but without my cooperation. As long as we're aboard the Proteus, I make the policy decisions. We've gone through too much now to quit, so we go forward to the clot, whatever happens and whatever Carter orders.

Carter shouted, "Repeat last message."

"CANNIBALIZING WIRELESS TO REPAIR LASER. THIS IS LAST MESSAGE."

Reid said, blankly, "They're breaking communication."

Carter said, "What happened to the laser?"

"Don't ask me."

Carter sat down heavily. "Have coffee brought up here, will you, Don? If I thought I could get away with it, I'd ask for a double scotch and soda, and then two more. We're jinxed!"

Reid had signalled for coffee. He said, "Sabotage, maybe."

"Sabotage?"

"Yes, and don't play innocent, general. You anticipated the possibility from the start, or why send Grant?"

"After what happened to Benes on the way here . . ."

"I know. And I don't particularly trust Duval or the girl, either."

"They're all right," said Carter, with a grimace. "They've got to be. Everyone here has to be right. There is no way to make security more secure."

"Exactly. No security procedure lends absolute certainty."

"All these people work here."

"Not Grant," said Reid.

"Eh?"

"Grant doesn't work here. He's an outsider."

Carter smiled spasmodically. "He's a government agent."

Reid said, "I know. And agents can play double games. You put Grant on the Proteus and a string of bad luck begins-or what looks like bad luck ..."

The coffee had come. Carter said, "That's ridiculous. I know the man. He's no stranger to me."

"When was the last time you saw him? What do you know about his inner life?"

"Forget it. It's impossible." But Carter stirred the cream into his coffee with a marked uneasiness.

Reid said, "All right. Just thinking out loud."

Carter said, "Are they still in the pleura?"

"Yes!"

Carter looked at the Time Recorder, which said 32, and shook his head in frustration.

Grant had the wireless in fragments before him. Cora looked at the transistors one after the other, turning them, weighing them, seeming almost to peer within them.

"This one," she said, doubtfully, "will do, I think, but that wire is much too thick."

Duval placed the wire under question on the illuminated opal glass and placed the damaged fragment of original wire next to it, comparing them with somber eyes.

Grant said, "There's nothing closer. You'll have to make it do."

"It's easy to say that," said Cora. "You can give me an order like that, but you can't give such an order to the wire. It won't work no matter how hard you shout at it."

"All right. All right." Grant tried to think and got nowhere.

Duval said, "Now wait. With luck, I may be able to scrape it thin enough. , Miss Peterson, get me a number eleven scalpel."

He placed the wire from what had been Grant's device (now wireless in literal truth) in two small clamps and swung a magnifying glass before it. He reached out for the scalpel which Cora placed within his grip and slowly, he began to scrape.

Without looking up, he said, "Kindly take your seat, Grant. You cannot help me by snorting over my shoulder."

Grant flinched a little, caught Cora's look of appeal. He said nothing and moved back to his seat.

Michaels, in his seat, greeted him humorlessly. "The surgeon is at work," he said. "The scalpel is in his hand and his temperament is at once at its full bent. Don't waste your time being angry with him."

Grant said, "I'm not angry with him."

Michaels said, "Of course you are, unless you're prepared to tell me you've resigned from the human race. Duval has the gift-the God-given gift, I'm sure he would say-of antagonizing people with a single word, a glance, a gesture. And if that weren't enough, there is the young lady."

Grant turned to Michaels with clear impatience. "What about the young lady?"

"Come now, Grant. Do you want a lecture on boys and girls?"

Grant frowned and turned away.

Michaels said softly, rather sadly, "You're in a quandary about her, aren't you?"

"What quandary?"

"She's a nice girl, very good-looking. And yet you're a professionally suspicious person."

"Well?"

"Well! What happened to the laser? Was it an accident?"

"It could have been."

"Yes, it could have been." Michaels' voice was a bare whisper. "But was it?"

Grant whispered, too, after a quick glance over his shoulder. "Are you accusing Miss Peterson of sabotaging the mission?"

"Of course not. I have no evidence of that. But I suspect you are accusing her in your mind and you don't like to be doing so. Hence the quandary."

"Why Miss Peterson?"

"Why not? Nobody would pay any attention to her if she were seen fiddling with the laser. It is her province. And if she were intent on sabotage, she would naturally gravitate to that part of the mission with which she felt most at home-the laser."

"Which would place immediate and automatic suspicion upon her-as it seems to have done," said Grant, with some heat.

"I see. You are angry."

Grant said, "Look. We're all in one relatively small ship and you might think that we were each of us under the close and constant observation of the others, but that's not so. We've been so absorbed with what's out there, all of us, that any one of us could have walked back to the storage compartment and done anything he wanted to the laser and done so unnoticed. You or I might have done it. I wouldn't have seen you. You wouldn't have seen me."

"Or Duval?"

"Or Duval. I'm not eliminating him. Or it might have been an honest accident."

"And your lifeline coming loose? Another accident?"

"Are you prepared to suggest anything else."

"No, I'm not. I can point out a few things, if you're in the mood."

"I'm not, but point them out anyway."

"It was Duval who secured your lifeline."

"And apparently made a poor knot, I suppose," said Grant. "Still there was considerable tension of the line. Considerable."

"A surgeon should be able to tie knots."

"That's nonsense. Surgical knots are not sailors' knots."

"Perhaps. On the other hand, maybe the knot was deliberately tied so as to come loose. Or perhaps it could have been untied by hand."

Grant nodded. "All right. But there again, everyone had their attention on what was going on about them. You, or Duval, or Miss Peterson, might have moved quickly back to the ship, loosened the knot, and returned without being noticed. Even ' Owens might have left the ship for the purpose, I suppose."

"Yes, but Duval had the best chance. Just before you broke loose, he went back to the ship, carrying the snorkel. He said the lifeline came loose as he watched. We know by his own admission that he was in the right place at the right time."

"And it might still have been an accident. What's his motive? The laser had already been sabotaged, and all he could accomplish by loosening the lifeline would be to endanger me personally. If he was after the mission, why bother with me?

"Oh, Grant! Oh, Grant!" Michaels smiled and shook his head.

"Well, talk. Don't just grunt."

"Suppose it was the young lady who took care of the laser. And suppose Duval's interest was specifically you; suppose he wanted to get rid of you, with damage to the mission strictly secondary."

Grant stared speechlessly.

Michaels went on. "Duval is perhaps not so entirely devoted to his work that he doesn't notice his assistant seems aware of your existence. You are a fine-looking young man, Grant, and you have saved her serious injury at the time of the whirlpool; perhaps even her life. Duval watched that and he must have watched her reaction."

"There was no reaction. She's not interested in me."

"I watched her when you were lost in the alveolus. She was distraught. What was obvious to anyone then, might have been obvious to Duval much sooner-that she was attracted to you. And he might have gotten rid of you for that reason."

Grant bit at his lower lip in thought, then said, "All right. And the loss of air. Was that an accident, too?"

Michaels shrugged. "I don't know. I suspect you will suggest that Owens might have been responsible for that."

"He might. He knows the ship. He designed it. He can best gimmick its controls. And only he checked on what was wrong."

"That's right, you know. That's right."

"And for that matter," went on Grant with gathering anger, "what about the arterio-venous fistula? Was that an accident, or did you know it was there?"

Michaels sat back in his chair and looked blank. "Good Lord, I hadn't thought of that. I give you my word, Grant, I sat here and honestly thought there wasn't a thing that happened that could possibly point in my direction specifically. I realized that it could be maintained that I had slyly damaged the laser or undone your lifeline knot or jammed the air chamber valve when no one was looking-or all three, for that matter. But in each case it was so much more likely that someone else had done it. The fistula, I admit, could be no one but myself."

"That's right."

"Except, of course, that I didn't know it was there. But I can't prove that, can I?"

"No."

Michaels said, "Do you ever read detective stories, Grant?"

"In my younger days I read quite a few. Now ..."

"Your profession spoils the fun. Yes, I can well imagine that. But you know, in detective stories, it is always so simple. A subtle clue points to one person and one person only and the detective sees it though no one else does. In real life, it seems, the clues point everywhere."

"Or nowhere," said Grant, firmly. "We could be dealing with a series of accidents and misfortunes."

"We could," conceded Michaels.

Neither, however, sounded very convincing. -Or convinced.