I threw the receiving switch.

"For heaven's sake!" I shouted in exasperation—an exasperation, I was dimly aware, shared by all the others who were leaning forward to hear Hillcrest's voice. "What are you talking about? What was the plane carrying? Over."

"Sorry. It's a guided-missile mechanism of such advanced design and so top-secret that its details, I gather, are known only to a handful of scientists in all the United States. It's the only one of its kind, and was being sent to Britain for study under the recent agreement to share knowledge on atomic weapons and guided missiles." Hillcrest's voice was calm now, measured and sober.

There was a pause, then he went on, slowly, impressively. "I understand the governments concerned are prepared to go any lengths—any lengths—to secure the recovery of this mechanism and prevent its falling into wrong hands."

There was another, longer pause: Hillcrest, clearly, was giving me an opportunity to say something, but I just didn't know what to say. The magnitude of the entire thing took my breath away, temporarily inhibited all thought and speech. . . . Hillcrest's voice was coming through again:

To help you identify this mechanism, Dr Mason. It's camouflaged, made up to look like an ebonite and metal portable radio of fairly large size, with a braided leather carrying strap. Find that portable, Dr Mason, and you'll—"

I never heard the end of that sentence. I was still sitting there, dazedly wondering why the words 'portable radio' should have triggered off such a clangorous bell in my mind -1 can only plead my extreme physical and mental exhaustion—when Zagero catapulted himself off his seat on the sled, knocking Jackstraw staggering, took one tremendous hop with his bound feet just opposite where I was sitting and hurled himself bodily towards Corazzini who, his face twisted in a vicious and unrecognisable mask, had pushed himself off the tractor tailboard with one hand and with the other was fumbling desperately to bring something out from under his coat. He saw he couldn't make it in time, threw himself to one side, but Zagero, bound though he was, was like a cat on his feet and I knew that instant, that instant that was too late, that Zagero was indeed the world-class boxer that he claimed to be. If the astonishing speed of his reflexes were not proof enough, that blurring right arm of his carried with it lethal conviction. Corazzini was a very big man, six feet two and at least two hundred pounds and he was swathed in many layers of heavy clothing, but when that fist caught him with such frightening power just under the heart he staggered back against the tailboard and slid slowly to the ground, unseeing eyes turned up to the first driving flakes of the newly fallen snow. I had never seen a blow delivered with such power: nor do I ever want to see it again.

For perhaps five seconds no one moved, no one spoke, men were held in thrall. The soughing, wailing moan of the wind on the ice-cap sounded weirdly, unnaturally loud. I was the first to break the silence. I was still sitting on my canvas stool.

"Corazzini!" I said. "Corazzini!" My voice was barely more than a whisper, but Zagero heard me.

"Sure it's Corazzini," he said levelly. "It always was." He stooped, thrust his hand under the unconscious man's coat and brought out his gun. "You'd better keep this, Doc. Not only do I not trust our little playmate here with toys like these, but the state prosecutor or district attorney or whatever you call the guy in England will find that the riflin' on this barrel matches the riflin' marks on some very interestin' bullets."

He tossed the gun across, and automatically I caught it. It was a pistol, not an automatic, and it had a strange-looking cylinder screwed on to the front of the barrel. A silencer, I supposed; I had never seen one before. Nor had I ever seen that type of gun before. I didn't like the look of it at all, and I guessed it might be wise to have a gun in my hand when Corazzini came round. Jackstraw, I could see, already had his rifle lined up on the unconscious man. I placed the pistol on the ground beside me and pulled out the Beretta.

"You were ready for him." I was still trying to put things in order in my own mind. "You were waiting for the break. How—"

"Do I have to draw a diagram, Doc?" There was no insolence in his voice, only weariness. "I knew it wasn't me. I knew it wasn't Solly. So it had to be Corazzini."

"Yes, I see. It had to be Corazzini." The words were automatic, meaningless. My thoughts were in a state of utter confusion, as confused, no doubt, as those of Corazzini who was now pushing himself groggily into a sitting position, but for the past fifteen seconds another bell had been ringing far back in my mind, not so loud as the first but even more desperately insistent, and all at once I had it and began to rise to my feet. "But there were two of them, two of them! Corazzini had an accomplice—" That was as far as I got when some metal object smashed across my wrist with brutal force, sending my Beretta flying, and something small and hard ground viciously into the back of my neck.

"Don't move, Dr Mason." The voice, flat, controlled but alive with a vibrant power that I had never heard before, was almost unrecognisable as the Rev. Joseph Smallwood's. "Nobody is to move. Nielsen, drop that rifle—now! Just one suspicious move and Dr Mason gets his head blown off."

I stood stock-still. The man behind that voice meant every word he said. I didn't need any convincing of that. The cold certainty in his voice only reinforced the knowledge I already had that the sanctity of human life was a factor which could never enter into this man's considerations.

"All right, Corazzini?" Smallwood was speaking again, his voice empty of all concern for and interest in his accomplice: his only anxiety, if one could by any stretch of imagination call it that, lay in his desire for Corazzini's effectively continued co-operation.

"All right," Corazzini said softly. He was standing now and that both mind and reactions were back to normal was evident from the dexterity with which he caught the gun Smallwood threw back to him. "Never thought any man could move so fast with his feet tied. But he won't catch me again. Everybody out, eh?"

"Everybody out," Smallwood nodded. No question, he was the leader of the two, ridiculously improbable though that would have seemed only two minutes ago: but it didn't seem improbable any longer, it seemed inevitable.

"Jump down! All of you," Corazzini ordered. Gun in one hand, he held back a flap of canvas screen with the other. "Hurry it up."

"Mahler can't jump down," I protested. "He can't move—he's in coma. He—"

"Shut up!" Corazzini interrupted. "All right, Zagero, inside and get him out."

"You can't move him!" I shouted furiously. "You'll kill him if—" My last word was choked off in a grunt of pain as Smallwood's gun barrel caught me viciously across the side of the head. I fell to my hands and knees in the snow and remained there for several seconds, head down and shaking it from side to side as I tried to overcome the dizziness and the pain.

"Corazzini said 'shut up'. You must learn to listen." Small-wood's voice was chillingly devoid of all emphasis and inflection. He stood waiting quietly until the last of the passengers had descended or been carried from the tractor cabin, then waved us all into a straight line facing towards Corazzini and himself. Both of them had their backs to the canvas screen, while we were placed just far enough clear of the shelter to be blinded by the increasingly heavy snowfall that swirled down into our eyes, but not so far off as not to be clearly seen by them. Whatever these two did, I was beginning to discover, betrayed that economy of movement and unquestioning sureness of the complete professionals who had long ago worked out the answers to and counters against any of a vast range and permutation of situations they were ever likely to encounter.

Smallwood beckoned me.

"You haven't finished your radio call, Dr Mason. Finish it. Your friend Hillcrest must be wondering at the delay." The gun in his hand came forward a fraction of an inch, just enough for the movement to be perceptible. Tor your own sake, do nothing to arouse his suspicions. Don't be clever. Keep it brief."

I kept it brief. I excused the interruption of transmission on the grounds that Mahler had taken a sudden turn for the worse—as indeed, I thought bitterly, he had—said that I'd guard the missile mechanism with my life and apologised for cutting the call short, but said it was essential to get Mahler to Uplavnik with all speed.

"Finish it off," Smallwood said softly in my ear. I nodded.

"That's the lot then, Captain Hillcrest. Will make the noon schedule. This is Mayday signing off. Mayday, Mayday."

I switched off, and turned indifferently away. I had taken only one step when Smallwood caught my shoulder and whirled me round. For such an apparently slight man, he was phenomenally strong. I gasped as his pistol barrel dug into my stomach.

" 'Mayday', Dr Mason?" he asked silkily. "What is 'Mayday'?"

"Our call-sign, of course," I said irritably.

"Your call-sign is GFK."

"Our call-up is GFK. Our signing-off is 'Mayday'."

"You're lying." I wondered how I could ever have thought this face meek and nervous and colourless. The mouth was a thin hard line, the upper eyelids bar-straight and hooded above the unwinking eyes. Flat marbled eyes of a faded light-blue. A killer's eyes. "You're lying," he repeated.

"I'm not lying," I said angrily.

"Count five and die." His eyes never left mine, the pressure of the gun increased. "One . . . two . . . three—"

"I'll tell you what it is!" The cry came from Margaret Ross. 'Mayday' is the international air distress signal, the SOS... I had to tell him, Dr Mason, I had to!" Her voice was a shaking sob. "He was going to kill you."

"I was indeed," Smallwood agreed. If he felt either anger or apprehension, no trace of either appeared in the calm conversational voice. "I should do it now—you've lost us four hours' head start. But courage happens to be one of the few virtues I admire. . . . You are an extremely brave man, Dr Mason. Your courage is a fair match for your—ah—lack of perspicacity, shall we say."

"You'll never get off the ice-cap, Small wood," I said steadily. "Scores of ships and planes are searching for you, thousands of men. They'll get you and they'll hang you for these five dead men."

"We shall see." He gave a wintry smile, and now that he had removed his rimless glasses I could see that the man's smile left his eyes untouched, left them flat and empty and lifeless, like the stained glass in a church and no sun behind it. "All right, Corazzini, the box. Dr Mason, bring one of the maps from the driver's seat."

"In a moment. Perhaps you would care to explain—"

"Explanations are for children." The voice was level, curt, devoid of all inflection." I'm in a hurry, Dr Mason. Bring the map."