Such, at least, was the theory, although Hillcrest didn't seem absolutely sure of himself. He had asked if we had any suggestion, whether we could help him in any way at all, but I had said we couldn't. I was tragically, unforgivably wrong. I could have helped, for I knew something that no one else did, but, at the moment, I completely forgot it. And because I forgot, nothing could now avert the tragedy that was to come, or save the lives of those who were about to die.
My thoughts were black and bitter as the tractor roared and lurched and clattered its way south-west by west under the deepening darkness of a sky that was slowly beginning to fill with cloud. A dark depression filled me, and a cold rage, and there was room in my mind for both. I had a strange fey sense of impending disaster, and though I was doctor enough to know that it was almost certainly a psychologically induced reaction to the cold, exhaustion, sleeplessness and hunger - and a physical reaction to the blow on the head - nevertheless I could not shake it off: and I was angry because I was helpless.
I was helpless to do anything to protect any of the innocent people with me, the people who had entrusted themselves to my care, the sick Mahler and Marie LeGarde, the quiet young German girl, the grave-faced Margaret Ross - above all, I had to admit to myself, Margaret Ross: I was helpless because I knew the murderers might strike at any time, for all I knew they might believe that Hillcrest had already told me all I needed to know ana that I was just waiting my chance to catch them completely off guard; on the other hand they, too, were almost certainly just biding their time, not knowing how much I knew, but just taking a calculated gamble, letting things ride as long as the tractor kept moving, kept heading in the right direction, but prepared to strike once and for all when the time came: and, above all, I was helpless because I still had no definite idea as to who the killers were.
For the hundredth time I went over everything I could remember, everything that had happened, everything that had been said, trying to dredge up from the depths of memory one single fact, one isolated word that would point the finger in one unmistakable direction. But I found nothing.
Of the ten passengers Jackstraw and I had with us, six of them, I felt certain, were almost beyond suspicion. Margaret Ross and Marie LeGarde were completely beyond it. The only things that could be said against Mrs Dansby-Gregg and Helene was that I hadn't absolute proof of their innocence, but I was certain that such proof was quite unnecessary. United States senators, as recent bribery and corruption cases had lamentably shown, had as many human failings - especially cupidity - as the next man: but, even so, the idea of a senator getting mixed up with murder and criminal activities on this massive scale was too preposterous to bear further examination. As for Mahler, I was quite aware that being a diabetic didn't bar a man from criminal pursuits, and he could have been one of the guilty men - just possibly, he had thought they would force-land near some easily available insulin supplies. But that was just a little too far-fetched, and even if it weren't, I wasn't seriously interested in Mahler. I was concerned with killers who might kill again at any moment, and he most certainly wasn't included in that category: Mahler was a dying man.
That left only Zagero, Solly Levin, Corazzini and the Rev. Smallwood, and the Rev. Smallwood was too good notto be true. The Bible was hardly ever out of his hands these days: there were certain lengths to which any impostor might reasonably be expected to go to convince us of his identity, but lengths such as these passed the bounds of the superfluous into the realms of the ridiculous.
I had reason to suspect Corazzini. As a tractor specialist, he knew precious little about tractors - although I had to be fair and admit that Citroen and Global tractors were a quarter of a century different in time and a world different in design. But he had been the only person I had found on his feet when I had opened the door of the passenger cabin in the plane. It was he who, back in the IGY cabin, had questioned me so closely about Hillcrest's movements. It was he, I had learnt, who had helped Jackstraw and Zagero bring up the petrol from the tunnel and so had the opportunity to spike the stuff left behind. Finally, I believed he could be utterly ruthless. But there was one great point in his favour: that still-bandaged hand, token of his desperate attempt to save the falling radio.
I had far greater reason to suspect Zagero, and, by implication of friendship, Solly Levin. Zagero had inquired of Margaret Ross when dinner was: a damning point. Solly Levin had been nearest the radio, and in the right position for doing the damage when it had been destroyed: another damning point. Zagero had been one of those working with the petrol. And, most damning of all, Zagero bore no more resemblance to a boxer than Levin did to any boxing manager who had ever lived outside the pages of Damon Runyon. And, as a further negative mark against Zagero, I had Margaret Ross's word that Corazzini had never left his seat in the plane. That didn't, of course, necessarily exclude Corazzini, he could well have had an accomplice. But who could that accomplice be?
It was not until then that the chilling, frightening thought struck me that, because two guns had been used in the plane, I had assumed all along that there were only two criminals. There wasn't a shadow of evidence to suggest why there should not be more than two: why not three? Why not Corazzini, Zagero and Levin all in the conspiracy together? I thought over the implications of this for some minutes, and at the end I felt more helpless than ever, more weirdly certain of ultimate tragedy to come. Forcibly, almost, I had to remind myself that all three were not necessarily working together; but it was a possibility that had to be faced.
About three o'clock in the morning, still following the flag trail that stretched out interminably before us in the long rake of the headlights, we felt the tractor slow down and Jackstraw, who was driving at the time, change gear as we entered on the first gentle slope of the long foothills that led to the winding pass that cut the Vindeby Nunataks almost exactly in half. We could have gone round the Nunataks, but that would have wasted an entire day, perhaps two, and with the ten-mile route through the hills clearly marked, it was pointless to make a detour.
Two hours later, as the incline perceptibly steepened, the tractor treads began to slip and spin on the frozen snow, but by off-loading almost all the petrol and gear we carried on the tractor sled and stowing it inside the tractor cabin, we managed to build up enough weight to gain a purchase on the surface. Even so, progress was slow and difficult. We could only make ground by following a zigzag pattern, and it took us well over an hour to cover the last mile before the entrance to the pass. Here we halted, soon after seven o'clock in the morning. The pass was lined on one side by a deep crevasse in the ice that ran its entire length, and although not particularly treacherous the trail was difficult and dangerous enough to make me determined to wait for the two or three brief hours' light at the middle of the day.
While breakfast was being prepared, I looked at Mahler and Marie LeGarde. The steady rise in temperature - it was now less than -SOT - had done nothing to help either of them. Marie LeGarde looked as if she hadn't eaten in weeks, her face, pock-marked with sores and frostbite blisters, was appallingly thin and wasted, and the once sparkling eyes lack-lustre, pouched and filled and rimmed with blood. She hadn't spoken a word in ten hours, just sat there, in her increasingly rare moments of waking, shivering and staring ahead with sightless eyes. Theodore Mahler looked in better case than she, but I knew when his defences went down they would do so in a matter of hours. Despite all that we -or, rather, Margaret Ross - had done for him, the insidious talons of frostbite had already sunk deep into his feet, he had developed a very heavy cold - rare indeed in the Arctic, the seeds of it must have been sown before he had left New York - and he had neither the energy nor reserves to fight either that or the boils that were beginning to plague him. His breathing was difficult, the sweet ethereal odour of acetone very strong. He seemed wide awake and rational enough, superficially a much better going concern than Marie LeGarde, but I knew that the collapse, the preliminary to the true diabetic coma, might come at any time.
At eight o'clock Jackstraw and I moved out on to the hillside, and again made contact with Hillcrest. My heart sank when I heard the grim news that they'd hardly progressed a couple of miles in the previous twelve hours. In that bitter cold, it seemed -and where they were temperatures were all of thirty degrees lower than they were with us - heating up an eight gallon drum of petrol, even using stoves, blow-lamps and every means at their disposal, to the point of boiling was a heartbreakingly slow job, and the Sno-Cat gobbled up in a minute all the pure fuel they could distil in thirty times that. Beyond that, there was no news: Uplavnik, which they had contacted less than an hour previously, had still nothing fresh to report. Without a word, Jackstraw and I packed up the equipment and made our way back to the cabin of the tractor. Jackstraw's almost invariable Eskimo cheerfulness was at the lowest ebb I had ever seen, he seldom spoke now and even more rarely smiled. As for me, I felt our last hope was gone.
We started up the tractor again at eleven o'clock and headed straight into the pass, myself at the wheel. I was the only person left in either the driving compartment or the cabin behind: Mahler and Marie LeGarde, vanished under a great mound of clothing, rode on the dog-sled while the others walked. The tractor was wide, the trail narrow and sometimes sloping outwards and downwards, and with a sideslip into the gaping crevasse that bordered our path nobody inside the cabin would have had any chance of escape.
The first part was easy. The trail, sometimes not more than eight or nine feet broad, more often than not opened out into a shelf wide enough, almost, to be called the flat floor of a valley, and we made rapid progress. At noon - I'd warned Hillcrest that we would be traversing the Vindeby Nunataks then and would have to miss our regular radio schedule - we were more than half-way through and had just entered the narrowest and most forbidding defile in the entire crossing when Corazzini came running up alongside the tractor and waved me down to a stop. I suppose he must have been shouting but I'd heard nothing above the steady roar of the engine: and, of course, I'd seen nothing, because they had all been behind me and the width of the tractor cabin made my driving mirror useless.
Trouble, Doc," he said swiftly, just as the engine died. "Someone's gone over the edge. Come on. Quick!"
"Who?" I jumped out of the seat, forgetting all about the gun I habitually carried in the door compartment as an insurance against surprise attack when I was driving. "How did it happen?"
"The German girl." We were running side by side round a corner in the track towards the little knot of people forty yards back, clustering round a spot on the edge of the crevasse. "Slipped, fell, I dunno. Your friend's gone over after her."
"Gone after her!" I knew that crevasse was virtually bottomless. "Good God!"
I pushed Brewster and Levin to one side, peered gingerly over the edge into the blue-green depths below, then drew in my breath sharply. To the right, as I looked, the gleaming walls of the crevasse, their top ten feet glittering with a beaded crystalline substance like icing sugar, and here not more than seven or eight feet apart, stretched down into the illimitable darkness, curving away from one another to form an immense cavern the size of which I couldn't even begin to guess at. To the left, more directly below, at a depth of perhaps twenty feet, the two walls were joined by a snow and ice bridge, maybe fifteen feet long, one of the many that dotted the crevasse through its entire length. Jackstraw was standing on this pressed closely into one edge, holding an obviously dazed Helene in the crook of his right arm.
It wasn't hard to work out Jackstraw's presence there. Normally, he was far too careful a man to venture near a crevasse without a rope, and certainly far too experienced to trust himself to the treachery of a snow-bridge. But, when Helene had stumbled over the edge, she must have fallen heavily - almost certainly in an effort to protect her broken collar-bone - and when she had risen to her feet had been so dazed that Jackstraw, to prevent her staggering over the edge of the snow-bridge to her death, had taken the near-suicidal gamble of jumping after her to stop her. Even in that moment I wondered if I would have had the courage to do the same myself. I didn't think so.
"Are you all right?" I shouted.
"I think my left arm is broken," Jackstraw said conversationally. "Would you please hurry, Dr Mason? This bridge is rotten, and I can feel it going."
His arm broken and the bridge going - and, indeed, I could see chunks of ice and snow falling off from the underside of the arch on which he was standing! The matter-of-fact lack of emotion of his voice was more compelling than the most urgent cry could possibly have been. But for the moment I was in the grip of a blind panic that inhibited all feeling, all thought except the purely destructive. Ropes - but Jackstraw couldn't tie a rope round himself, not with an arm gone, the girl couldn't help herself either, both of them were helpless, somebody would have to go down to them, and go at once. Even as I stared into the crevasse, held in this strange motionless thrall, a large chunk of niv6 broke off from the side of the bridge and plummeted slowly down into the depths, to vanish from sight, perhaps two hundred feet below, long before we heard it strike the floor of the crevasse.