"There was a trickle from the test cock in number 4 tube," Hansen objected. -

"Low-grade chewing gum."

"The murderous swine," Swanson said calmly. His restraint was far more effective than the most thunderous denunciations could ever have been. "He could have murdered us all. But for the grace of God and the Groton boatyard shipwrights, he would have murdered us all."

"He didn't mean to," I said. "He didn't mean to kill anyone. You had intended to carry out a slow-time dive to check trim in the Holy Loch before you left that evening. You told me so yourself. Did you announce it to the crew, post it up in daily orders or something like that?"

"Both."

"So. Our pal knew. He also knew that you would carry out those checks when the boat was still awash or just under the surface. When you checked the tubes to see if they were okay, water would come in, too much water to permit the rear doors to be shut again, but not under such high pressure that you wouldn't have time and enough to spare to close the fo'ard collision-bulkhead door and make a leisurely retreat in good order. What would have happened? Not much. At the worst you would have settled down slowly to the bottom and stayed there. Not deep enough to worry the Dolphin. In a submarine of even ten years ago it might have been fatal for all, because of the limited air supply. Not today, when your air-purifying machines can let' you stay down for months at a time. You just float up your emergency-indicator buoy and telephone, tell your story, sit around and drink coffee till a naval diver comes down and replaces the bow cap, pump out the torpedo room and surface again. Our unknown pal — or pals — didn't mean to kill anyone. But they did mean to delay you. And they would have delayed you. We know now that you could have got to the surface under your own steam, but, even so, your top brass would have insisted that you go into dock for a day or two to check that everything was okay."

"Why should anyone want to delay us?" Swanson asked. I thought he had an unnecessarily speculative look in his eyes, but it was hard to be sure; Commander Swanson's face showed exactly what Commander Swanson wanted it to show and no more.

"My God, do you think I know the answer to that one?" I said irritably.

"No. No, I don't think so." He could have been more emphatic about it. "Tell me, Dr. Carpenter, do you suspect some member of the «Dolphin's» crew to be responsible?"

"Do you really need an answer to-that one?"

"I suppose not," he sighed. "Going to the bottom of the Arctic Ocean is not a very attractive way of committing suicide, and if any member of the crew had jinxed things, he'd damn soon have unjinxed them as soon as he realized that we weren't going to carry out trim checks in shallow water. Which leaves only the civilian dockyard workers in Scotland — and every one of them had been checked and rechecked and given a top-grade security clearance."

"Which means nothing. There are plushy Moscow hotels and British and American prisons full of people who had top-grade security clearances… What are you going to do now, Commander? About the «Dolphin», I mean?"

"I've been thinking about it. In the normal course of events the thing to do would be to close the bow cap of number 4 and pump out the torpedo room, then go in and close the rear door of number 4. But the bow-cap door won't close. Within a second of John's telling us that number 4 was open to the sea, the diving officer hit the hydraulic button — the one that closes it by remote control. You saw for yourself that nothing happened. It must be jammed."

"You bet your life it's jammed," I said grimly. "A sledge hammer might do some good, but pressing buttons won't."

"I could go back to that lead we've just left, surface again, and send a diver under the ice to investigate and see what he can do, but I'm not going to ask any man to risk his life doing that. I could retreat to the open sea, surface, and fix it there, but not only would it be a damned slow and uncomfortable trip with the «Dolphin» canted at this angle, it might take us days before we got back here again. And some of the Drift Station Zebra men are pretty far gone. It might he too late."

"Well, then," I said. "You have the man at hand, Commander. I told you when I first met you that environmental health studies were my specialty, especially in the field of pressure extremes when escaping from submarines. I've done an awful lot of simulated sub escapes, Commander. I do know a fair amount about pressures, how to cope with them and how I react to them myself."

"How do you react to them, Dr. Carpenter?"

"A high tolerance. They don't worry me much."

"What do you have in mind?"

"You know damn well what I have in mind," I said impatiently. "Drill a hole in the door of the after collision bulkhead, screw in a high-pressure hose, open the door, shove someone in the narrow space between the two collision bulkheads, and turn up the hose until the pressure between the collision bulltheads equals that in the torpedo room. You have the clips eased off the for'ard collision door. When the pressures are equalized, it opens at a touch, you walk inside, close number 4 rear door, and walk away again. That's what you had in mind, wasn't it?"

"More or less," he admitted. "Except that «you» are no part of it. Every man on this• ship has made simulated escapes. They all know the effects of pressure. And most of them are a great deal younger than you."

"Suit yourself," I said. "But age has little to do with the ability to stand stresses. You didn't pick a teen-ager as the first American to orbit the earth, did you? As for simulated escapes, making a free ascent up a hundred-foot tank is a different matter altogether from going inside an iron box, waiting for the slow build-up of pressure, working under that pressure, then waiting for the slow process of decompression. I've seen young men, big, tough, very, very fit young men break up completely under those circumstances and almost go crazy trying to get out. The combination of physiological and psychological factors involved is pretty fierce."

"I think," Swanson said slowly, "that I'd sooner have you — what do the English say, 'batting on a sticky wicket'? — than almost any man I know. But there's a point you've overlooked. What would the Commander of Atlantic Submarines say to me if he knew I'd let a civilian go instead of one of my own men?"

"If you «don't» let me go, I know what he'll say. He'll say, 'We must reduce Commander Swanson to lieutenant, j.g., because he had on board the «Dolphin» an acknowledged expert in this specialty and refused, out of stiff-necked pride, to use him, thereby endangering the lives of his crew and the safety of his ship.'

Swanson smiled, a pretty bleak smile, but with the desperately narrow escape we had just had, the predicament we were still in, and the fact that his torpedo officer was lying dead not so many feet away, I hardly expected him to break into gales of laughter. He looked at Hansen. "What do you say, John?"

"I've seen more incompetent characters than Dr. Carpenter," Hansen said. "Also, he gets about as nervous and panicstricken as a bag of Portland cement."

"He has qualifications you don't expect to find in the average medical man," Swanson agreed. "I shall be glad to accept your offer. One of my men will go with you. That way the dictates of common sense and honor are both satisfied."

It wasn't all that pleasant, not by a long shot, but it wasn't all that terribly bad, either. It went off exactly as it could have been predicted it would go off. Swanson cautiously eased the «Dolphin» up until her stern was just a few feet beneath the ice; this reduced the pressure in the torpedo room to a minimum, but even at that the bows were still about a hundred feet down.

A hole was drilled in the after collision bulkhead door and an armored high-pressure hose screwed into position. Dressed in porous rubber suits and equipped with an aqualung apiece, a young torpedoman by the name of Murphy and I went inside and stood in the gap between the two collision bulkheads. High-powered air hissed into the confined space. Slowly the pressure rose: twenty, thirty, forty, fifty pounds to the square inch. I could feel the pressure on lungs and ears, the pain behind the ears, the slight wooziness that comes from the poisonous effect of breathing pure oxygen under such pressure. But I was used to it; I knew it wasn't going to kill me. I wondered if young Murphy knew that. This was the stage where the combined physical and mental effects became too much for most people, but if Murphy was scared or panicky or suffering from bodily distress, he hid it well. Swanson would have picked his best man, and to be the best man in a company like that, Murphy had to be something very special.