"Still hear it?"

"Getting louder all the time, Dr Mason. Louder and closer."

I wondered vaguely—vaguely and a trifle irritably, for this was our world, a tightly-knit, compact little world, and visitors weren't welcome—what plane it could be. A met. plane from Thule, possibly. Possibly, but unlikely: Thule was all of six hundred miles away, and our own weather reports went there three times a day. Or perhaps a Strategic Air Command bomber testing out the DEW-line—the Americans' distant early warning radar system—or even some civilian proving flight on a new trans-polar route. Or maybe some base plane from down by Godthaab.

"Dr Mason!" Jackstraw's voice was quick, urgent. "It's in trouble, I think. It's circling us—lower and closer all the time. A big plane, I'm sure: many motors."

"Damn!" I said feelingly. I reached out for the silk gloves that always hung at night above my head, pulled them on, unzipped my sleeping-bag, swore under my breath as the freezing air struck at my shivering skin, and grabbed for my clothes. Half an hour only since I had put them off, but already they were stiff, awkward to handle and abominably cold—it was a rare day indeed when the temperature inside the cabin rose above freezing point. But I had them on—long underwear, woollen shirt, breeches, silk-lined woollen parka, two pairs of socks and my felt cabin shoes—in thirty seconds flat. In latitude 72.40 north, 8000 feet up on the Greenland ice-cap, self-preservation makes for a remarkable turn of speed. I crossed the cabin to where no more than a nose showed through a tiny gap in a sleeping-bag.

"Wake up, Joss." I shook him until he reached out a hand and pushed the hood off his dark tousled head. "Wake up, boy. It looks as if we might need you."