So Bronson left the house quickly. He was an interloper--and, though helpless to do anything but run, he was infinitely better off with his freedom than in capture, jail or, more probably, death. Killing him on his own world would bring about the rather complex problem of disposing of the corpse. While this is possible, it is difficult to dispose of such a high degree of absolute contraband in a civilization with which you are not over-familiar. So some lucky accident had brought Bronson into this ill-fated Earth Two in a residence instead of the laboratory or military establishments of the imminent invaders. * * * * * Outside, Bronson knew that something was wrong. He wondered what it was. It was vague, something that was missing from a mere sketchy description but something rather important from a secondary--or was it primary--viewpoint, something that did not jell. It was late afternoon. The sun was setting in the west. But there was no pillar of atomic fire in the sky! The Miss Carlson of Earth Two had said that all of Albuquerque was illuminated by the vastness of the pillar of incandescent flame that reached from horizon to the sky. Where in the name of thunder-- The whirling madness spiraled in Bronson's mind with the never-ending round of who, what, why, when and where. And driving that engine of madness was the ever-present and ever-growing fear that the earth he knew was threatened with death--while he could do nothing but stand by and watch it die. And join it.... The light disappeared like the snuffing of a candle, and Maddox turned to Kingston with a grim smile. "That's that," he said. Kingston nodded affably. "Now all we have to do is to complete our plans." Maddox shook his head. "Remember that the stuff in Bronson's laboratory is the only supercritical mass on Earth One. We can see through, of course, but without that focal point we cannot cross over." He turned and left the drone-control room, walking down the corridor towards the other laboratory with Kingston beside him. Kingston was silent for a moment. Then he nodded in self-satisfaction. "I'll send through a corps of guards to protect it until we need it." "Better yet," said Maddox, "send through a couple of technicians to separate it into subcritical masses until we need it. Then we can prevent Earth Two from crossing." They turned the corner of the hallway and entered the original laboratory. As they did so, Kingston caught the sight of the viewscreen and stopped short, his jaw dropping. On the screen was the view of Bronson's laboratory. Virginia was sitting idly in a chair watching the equipment. Her attitude was not one of complete relaxation, nor was it one of deep intent. Maddox and Kingston knew at once that Virginia was waiting while the equipment ran automatically.