O'Hara was cruising at two thousand miles an hour. His fuel gauges indicated that he might keep going for three thousand miles, depending on his altitude. It was necessary, he knew, to get above forty thousand feet and to stay there for his best distance, and he had to have distance toward the south--for the storms of December would have driven snow deep along the lost continent of North America. He was not equipped for any lengthy existence in snow. His craft had the Patrol's usual paraphernalia--an inflatable boat, a signal pistol, a .38 automatic with six clips of ammunition, emergency water supply, emergency rations, the items considered indispensable when a rescue team could be expected to begin search soon after he failed to report to his base at Wrangell Island. But now, south of the Curtain, no rescue team was coming. None could get through. In consequence, his life depended on getting below the wasteland of the Arctic. These things, O'Hara said, ticked automatically through his mind in those first few minutes after he realized that he had got through the Curtain--these, and the overwhelming importance of the fact itself, that the Curtain could be pierced. He had, of course, no idea how the thing had been achieved. It had happened while he was unconscious, but as he reasoned it, his craft must have spun from north to south and then rammed through. Nor had he any data on the milliroentgen count of the Curtain itself--he had no idea of the contamination to which he had been exposed. He realized that at this moment he should have been a charred mass of carbon, like the bodies of those men on Coronation Island, in the Antarctic, after their vessel of logs had drifted into the Curtain. But the indisputable fact remained that he was not carbonized. He could only accept it and take whatever precautions seemed most likely to keep him alive, which now, at this moment, seemed to call for flying south. Within minutes he was crossing a coastline, and following the bed of a frozen river that pointed roughly south. Far toward his right--the west--the saw-toothed stubs of mountains poked their glittering ice-sheathed peaks up from the continent, and O'Hara was remembering the maps he'd studied as a boy. That way, the west, must be Alaska. Again he checked his position in latitude and longitude, then deciding that the river course below him must be the Mackenzie, reaching down past Great Bear Lake in Canada toward Great Slave Lake. And somewhere distant past the snow-packed tundras toward the east would be the land-locked gulf of Hudson Bay.