The relayed radio message we had received just fortynine hours ago had been the last. Since then, there had been only silence. The trawler «Morning Star» had been sending almost continuously in the intervening two days, trying to raise Drift Station Zebra, but out of that bleak desert of ice to the north had come nothing but silence. No word, no signal, no faintest whisper of sound had come out of that desolation.

Eighteen hours before, the Russian atomic-engined «Dvina» had reached the Barrier and had started on an all-out and desperate attempt to smash its way into the heart of the ice cap. In this early stage of winter the ice was neither so thick nor so compacted as it would be at the time of its maximum density, in March, and the very heavily armored and powerfully engined «Dvina» was reputed to be able to break through ice up to a thickness of eighteen feet: given fair conditions, the «Dvina» was widely believed to be capable of battering its way to the North Pole. But the conditions of the rafted ice had proved abnormal to a degree and the attempt a hopeless one. The «Dvina» had managed to crash its way over forty miles into the ice cap before being permanently stopped by a thick wall of rafter ice over twenty feet in height and probably more than a hundred deep. The «Dvina», according to reports, had sustained heavy damage to its bows and was still in the process of extricating itself, with the greatest difficulty, from the pack. A very gallant effort that had achieved nothing except an improvement in East-West relations to an extent undreamed of for many years.

Nor had the Russians' efforts stopped there. Both they and the Americans had made several flights over the area with front-line long-range bombers. Through the deep overcast and driving ice and snow-filled winds, those planes had criss-crossed the suspected area a hundred times searching with their fantastically accurate radar. But not one single radar sighting had been reported. Various reasons had been put forward to explain the failure, especially the failure of the Strategic Air Command's B52 bomber whose radar was known to be easily capable of picking out a hut against contrasting background from ten thousand feet and in pitch darkness. It had been suggested that the huts were no longer there: that the radar's eye was unable to distinguish between an ice-sheathed hut and the thousands of ice hummocks that dot the polar cap in winter: and that they had been searching in the wrong area in the first place. The most probable explanation was that the radar waves had been blurred and deflected by the dense clouds of ice spicules blowing over the area. Whatever the reason, Drift Ice Station Zebra remained as silent as if no life bad ever been there, as lost as if it had never existed.

"There's no percentage in staying up here and getting frozen to death." Commander Swanson's voice was a half-shout, it had to be to make him heard. "If we're going under that ice, we might as well go now." He turned his back to the wind and stared out to the west where a big, broad-beamed trawler was rolling heavily and sluggishly in the seas less than a quarter of a mile away. The «Morning Star», which had closed right up to the edge of the ice pack over the last two days, listening, waiting, and all in vain, was about to return to Hull: her fuel reserves were running low.

"Send them this message," Swanson said to the seaman by his side. "'We are about to dive and proceed under the ice. We do not expect to emerge for minimum four days, are prepared to remain maximum fourteen.'" He turned to me and said, "If we can't find them in that time — " and left the sentence unfinished.

I nodded, and he went on with the message: "'Many thanks for your splendid co-operation. Good luck and a safe trip home.'" As the signalman's lamp started chattering out its message, he said wonderingly, "Do those fishermen trawl up in the Arctic the entire winter?"

"They do."

"The whole winter. Fifteen minutes and I'm about dead. Just a bunch of decadent limeys, that's what they are." A lamp aboard the «Morning Star» flickered for some seconds, and Swanson said, "What reply?"

"Mind your heads under that ice. Good luck and goodby."

"Everybody below," Swanson said. As the signalman began to strip the canvas dodger, I dropped down a ladder into a small compartment beneath, wriggled through a hatch and down a second ladder to the pressure hull of the submarine, another hatch, a third ladder, and then I was on the control deck of the «Dolphin». Swanson and the signalman followed, then last of all Hansen, who had to close the two heavy water-tight doors above.

Commander Swanson's diving technique would have proved a vast disappointment to those brought up on a diet of movie submarines. No frenzied activity, no tense, steely-eyed men hovering over controls, no dramatic calls of "Dive, dive, dive," no blaring of kiaxons. Swanson reached down a steel-spring microphone, said quietly, "This is the captain. We are about to move under the ice. Diving now," hung up and said: "Three hundred feet."

The chief electronics technician leisurely checked the rows of lights indicating all hatches, surface openings, and valves closed to the sea. The disc lights were out: the slot lights burned brightly. Just as leisurely he rechecked them, glanced at Swanson and said, "Straight line shut, sir." Swanson nodded. Air hissed loudly out of the ballast tanks, and that was it. We were on our way. It was about as wildly exciting as watching a man push a wheelbarrow. And there was something oddly reassuring about it all.

Ten minutes later Swanson came up to me. In the past two days I'd come to know Commander Swanson fairly well, like him a lot, and respect him tremendously. The crew had complete and implicit faith in him. I was beginning to have the same thing. He was a kindly, genial man with a vast knowledge of every aspect of submarining, a remarkable eye for detail, an even more remarkably acute mind and an imperturbability that remained absolute tinder all conditions. Hansen, his executive officer and clearly no respecter of persons, had said flatly that Swanson was the best submarine officer in the Navy. I hoped he was right; that was the kind of man I wanted around in conditions like these.

"We're about to move under the ice now, Dr. Carpenter," he said. "How do you feel about it?"

"I'd feel better if I could see where we were going."

"We can see," he said. "We've got the best eyes in the world aboard the «Dolphin». We've got eyes that look down, around, ahead, and straight up. Our downward eye is the fathometer, or echo-sounder, which tells us just how deep the water below our keel is and as we have about five thousand feet of water below our keel at this particular spot, we're hardly likely to bump into underwater projections and its use right now is purely a formality. But no responsible navigation officer would ever think of switching it off. We have two sonar eyes for looking around and ahead, one sweeping the ship, another searching out a fifteen-degree path on either side of the bow. Sees everything, hears everything. You drop a wrench on a warship twenty miles away and we know all about it. Fact. Again it seems purely a formality. The sonar is searching for underwater ice stalactites forced down by the pressure of rafted ice above, but in five trips under the ice and two to the Pole, I've never seen underwater stalactites or ridges deeper than two hundred feet, and we're at three hundred feet now. But we still keep them on."

"You might bump into a whale?" I suggested.

"We might bump into another submarine." He wasn't smiling. "And that would be the end of both of us. What with the Russian and our own nuclear submarines busy crisscrossing to and fro across the top of the world, the underside of the polar ice cap is getting more like Times Square every day."