Joss didn't reply at once. The implications of all this, as I'd found out for myself, took no little time for digestion, so I let him take his time and waited, listening to the lost and mournful wailing of the wind, the rustling hiss of millions of ice spicules scudding across the frozen snow of the ice-cap, and my own thoughts were in keeping with the bleak misery of the night.

"It's not possible," Joss muttered at length. I could hear his teeth chattering with the cold. "You can't have some maniac rushing around an aircraft cabin with a hypo needle or dropping fizz-balls into their gin and tonics. You think they were all doped?"

"Just about."

"But how could anyone – "

"A moment, Joss," I interrupted. "What happened to the RCA?"

"What?" The sudden switch caught him momentarily off-balance. "What happened – you mean, how did it go for a burton? I've no idea at all, sir. All I know is that these hinges couldn't have been knocked into the wall accidentally – not with radio and equipment weighing about 180 pounds sitting on top of them. Someone shoved them in. Deliberately."

"And the only person anywhere near it at the time was the stewardess, Margaret Ross. Everyone agreed on that."

"Yes, but why in the name of heaven should anyone want to do a crazy thing like that?"

"I don't know," I said wearily. "There's a hundred things I don't know. But I do know she did it.. . . And who's in the best position to spike the drinks of aircraft passengers?"

"Good God!" I could hear the sharp hissing intake of breath. "Of course. Drinks – or maybe the sweets they hand out at take-off."

"No." I shook my head definitely in the darkness. "Barley sugar is too weak a covering-up agent to disguise the taste of a drug. Coffee, more likely."

"It must have been her," Joss said slowly. "It must have been. But – but she acted as dazed and abnormal as any of the others. More so, if anything."

"Maybe she'd reason to," I said grimly. "Come on, let's get back or we'll freeze to death. Tell Jackstraw when you get him by himself."

Inside the cabin, I propped the hatch open a couple of inches -with fourteen people inside, extra ventilation was essential. Then I glanced at the thermograph: it showed 48° below zero – eighty degrees of frost.

I lay down on the floor, pulled my parka hood tight to keep my ears from freezing, and was asleep in a minute.

For the first time in four months I had forgotten to set the alarm-clock before I went to sleep, and it was late when I awoke, cold and stiff and sore all over from the uneven hardness of the wooden floor. It was still dark as midnight – two or three weeks had passed since the rim of the sun had shown above the horizon for the last time that year, and all the light we had each day was two or three hours dim twilight round noon – but a glance at the luminous face of my watch showed me that it was nine-thirty.

I pulled the torch out from my parka, located the oil-lamp and lit it. The light was dim, scarcely reaching the far corners of the cabin, but sufficient to show the mummy-like figures lying huddled on the bunks and sprawled grotesquely across the floor, their frozen breath clouding before their faces and above their heads, then condensing on the cabin walls. The walls themselves were sheeted with ice which had extended far out across the roof, in places reaching the skylights, a condition largely brought about by the cold heavy air that had flooded down the opened hatchway during the night: the outside temperature registered on the drum at 54° below zero.

Not everyone was asleep: most of them, I suspected, had slept but little, the numbing cold had seen to that: but they were as warm in their bunks as they would be anywhere else and nobody showed any inclination to move. Things would be better when the cabin heated up a little.

I had trouble starting the stove – even though it was gravity fed from a tank above and to one side of it, the fuel oil had thickened up in the cold – but when it did catch it went with a roar. I turned both burners up to maximum, put on the water bucket that had lain on the floor all night and was now nearly a solid mass of ice, pulled on snow-mask and goggles and clambered up the hatchway to have a look at the weather.

The wind had died away almost completely – I'd known that from the slow and dispirited clacking of the anemometer cups -and the ice-drift, which at times could reach up several hundred feet into the sky, was no more than gentle puffs of dust stirring lazily and spectrally, through the feeble beam of my torch, across the glittering surface of the ice-cap. The wind, such as it was, still held out to the east. The cold, too, was still intense, but more bearable than it had been on the previous night. In terms of the effect of cold on human beings in the Arctic, absolute temperature is far from being the deciding factor: wind is just as important -every extra mile per hour is equivalent to a one degree drop in temperature – and humidity far more so. Where the relative humidity is high, even a few degrees below zero can become intolerable. But today the wind was light and the air dry. Perhaps it was a good omen.. . . After that morning, I never believed in omens again.

When I got below, Jackstraw was on his feet, presiding over the coffee-pot. He smiled at me, and his face was as fresh and rested as if he'd had nine hours on a feather bed behind him. But then Jack-straw never showed fatigue or distress under any circumstances: his tolerance to sleeplessness and the most exhausting toil was phenomenal.

He was the only one on his feet, but far from the only one awake: of those in the bunks, only Senator Brewster was still asleep. The others were facing into the centre of the room, a few propped up on their elbows: all of them were shivering, and shivering violently, their faces blue and white and pinched with the cold. Some were looking at Jackstraw, wrinkling their noses in anticipation of the coffee, the pungent smell of which already filled the cabin; others were staring in fascination at the sight of the ice on the roof melting as the temperature rose, melting, dripping down to the floor in a dozen different places and there beginning to form tiny stalagmites of ice, building up perceptibly before their eyes: the temperature on the cabin floor must have been almost forty degrees lower than that at the roof.

"Good morning, Dr Mason." Marie LeGarde tried to smile at me, but it was a pathetic effort, and she looked ten years older than she had on the previous night: she was one of the few with a sleeping-bag, but even so she must have passed a miserable six hours, and there is nothing so exhausting to the human body as uncontrollable night-long shivering, a vicious circle in which the more one shivers the tireder one becomes, and the tireder the less resistance to cold and hence the more shivering. For the first time, I knew that Marie LeGarde was an old woman.

"Good morning," I smiled. "How did you enjoy your first night in your new home?"

"First night!" Even in the sleeping-bag her movements of clasping her arms together and huddling her head down between her shoulders were unmistakable. "I hope to heaven that it's the last night. You run a very chilly establishment here, Dr Mason."

"I'm sorry. Next time we'll keep watches and have the stove on all night." I pointed to the water splashing down to the floor. "The place is heating up already. You'll feel better when you have some hot coffee inside you."

"I'll never feel better again," she declared vigorously, but the twinkle was back in her eye. She turned to the young German girl in the next bunk. "And how do you feel this morning, my dear?"

"Better, thank you, Miss LeGarde." She seemed absurdly grateful that anyone should even bother to ask. "I don't feel a thing now."