I motioned him out of the way and had a look. Two seconds later I had thrust my automatic into Joss's hand and was on my way up top.

The airliner was a blazing torch in the darkness of the night. Even at that distance of half a mile and against the light wind, I could clearly hear the fierce roaring and crackling of the flames -not flames, rather, but one great solid column of fire that seemed to spring from the wings and centre of the fuselage and reach up clear and smokeless and sparkless two hundred feet into the night sky, brushing its blood-red stain across the snow for hundreds of yards around, transforming the rest of the still ice-sheathed fuselage into a vast effulgent diamond, a million constantly shifting points of refracted white and red and blue and green that glittered and gleamed with an eye-dazzling scintillating brilliance that no jewels on earth could have matched. It was a fantastically beautiful spectacle, but I'd had time to watch it for barely ten seconds when the dazzling coloured irradiation turned into a blaze of white, the central flame leapt up to twice, almost three times its original height and, two or three seconds later, the roar of the exploding petrol tanks came at me across the frozen stillness of the ice-cap.

Almost at once the flames seemed to collapse in upon themselves and the perimeter of the blood-red circle of snow shrank almost to vanishing point, but I waited to see no more. I dropped down into the cabin, pulling the hatch shut behind me, and looked at Jackstraw.

"Any chance at all of accounting for the presence of our various friends here during the past half-hour?"

"I'm afraid not, Dr Mason. Everyone was on the move all the time, finishing off the tractor body or bringing up the stores and petrol drums and lashing them on the sledge." He glanced up through the skylight. "The plane, wasn't it?"

" 'Was' is right." I glanced at the stewardess. "My apologies, Miss Ross. You did hear somebody out there."

"You mean—you mean it wasn't an accident?" Zagero asked.

There's a fair chance that you know damned well that it wasn't, I thought. Aloud, I said: "It was no accident."

"So there goes your evidence, eh?" Corazzini asked. "The pilot and Colonel Harrison, I mean."

"No. The nose and tail of the plane are still intact. I don't know what the reason could be—but I'm sure there's a damned good one. And you can put these bags away, Mr Corazzini. We're not, as you say, playing with children or amateurs."

There was silence while Corazzini returned the bags, then Joss looked at me quizzically.

"Well, that explains one thing at least."

"The messed-up explosives?" I remembered with chagrin how I had listened to the abnormally loud hissing out by the plane, but had ignored it. Someone who had known very clearly what he was doing had led a fuse into petrol lines or tanks or carburettors. "It certainly does."

"What's all this about explosives and fuses?" Senator Brewster demanded. It was the first word he had spoken since Jackstraw had scared the wits out of him, and even yet the colour wasn't all back in his face.

"Somebody stole the fuses to set fire to the plane. For all I know it may have been you." I held up my hand to still his outraged spluttering and went on wearily: "It may equally well have been one of the other seven of you. I don't know. All I know is that the person or persons responsible for the murders were responsible for the theft of the fuses. And for the smashing of the radio valves. And for the theft of the condensers."

"And for the theft of the sugar," Joss put in. "Though heaven only knows why they should want to steal that."

"Sugar!" I exclaimed, and then the question died in my throat. I happened to be looking straight at the little Jew, Theodore Mahler, and the nervous start he gave, the quick flicker of his eyes in Joss's direction, was unmistakable. I knew I couldn't have imagined it. But I looked away quickly, before he could see my face.

"Our last bag," Joss explained. "Maybe thirty pounds. It's gone. I found what little was left of it—just a handful lying on the floor of the tunnel—mixed up with the smashed valves."