For 130 minutes of continuous flying through this long corridor south of the Atomic Curtain the milliroentgen count had remained almost steady at .295, but at 2:30 P.M., and without an obvious physical reason for it, the count suddenly made an abrupt rise even at the 40,000-foot level at which he was flying. O'Hara tried swerving both to the east and west, also changing altitudes, but the contamination continued rising above .400 with every second's flying time. Here was a new phenomenon--a density of radiation that indicated some intense new barrier, and moments later O'Hara saw a strange, enormous white oblong reaching from east to west, not quite to the horizons but effectively spanning the area that he had determined composed the north-south corridor of least contamination. And such was the milliroentgen count that O'Hara felt it must in some way be a source--or excessive consumer--of atomic power. O'Hara's latitude calculation fixed his position as the southern part of the state of Colorado. The long corridor was in truth a closed rectangle, a box--a coffin without escape. He could only turn north again into it. But the arc of his explorations had swung him well toward the east, and in these seconds he passed once more above the ruined debris of an empty city, the same pattern of collapsed roofs and time-desiccated walls extending for miles around a single sky-piercing tower of stone and metal with that glass-encased solarium at its summit. And this time, although it was gone in an instant, a place name fixed itself in O'Hara's mind, corroborated by his memory of latitude and longitude--the sky-high city of Denver. His milliroentgen count was dropping back toward the .285 level he had anticipated, but all at once his motors cut out on him. His fuel was exhausted. "There are such things as heroes," said O'Hara, and paused, tilting back in the comfortable easy chair of his Bloomsbury flat, a fresh drink in his hand. He took a long pull at the glass, reflectively. And for a moment it was as if we were stepping back across the Atomic Curtain, both of us, back from the Lost Continent, taking within a second's time a giant stride from unreality into the stodginess of present-day London. O'Hara smiled crookedly. "Yes," he continued, "there are such things as heroes--Tournant is rather close to it, I think. He has the courage to do what he can do, and to reject what he cannot. That's a hero in my book. But I'm not and never was, and when I heard the last unhappy cough from my motors and realized quite definitely that I was in for it, my knees were wax. No, not that crusty--they were jelly. When I understood that I was going down and that my craft, which until then had given me some sense of decision, was nothing now, dead metal under me--well, fear does crazy things to you. I screamed. It's true, I bellowed like a gored ox, striking both fists at my altimeter, shattering it. Until at last the needle, broken, jammed."