"Now I'm not exactly convinced that Nature or God was baffled by this thing that His toy built and therefore held His benevolent--but baffled--hand in the stream of time to see which was the best. "I'm inclined to think there was a good scientific explanation of why time should have split three ways--why in one case the earth entered fission, why the thing worked properly in another time-stream and why the Alamogordo Bomb fizzled in a third." "Can you find out why--and what it could have been?" she asked. He laughed shortly. "It isn't mumbo-jumbo or magic," he said. "All of the things attributed to mumbo-jumbo are based upon facts not known to those who observe the effects. The very fact that there was some doubt about the outcome of the Alamogordo Bomb proved that the best brains knew their knowledge of nuclear physics was incomplete." Virginia nodded brightly. "So you think that some unknown factor caused the trouble?" "Obviously. We know that fissionable materials do operate. The Hiroshima and Nagasaki bombs were of different types of material, giving us at least two different proofs of its operation. We have too little knowledge of Earth Three but I'm reasonably certain that, once the original experiment failed, fissionable reactions took place and are taking place now. We know even less of the affair of Earth Two. We don't know but can assume that later attempts would turn out properly." Virginia said nothing. She nodded sagely, and her nod was based upon the fact that she knew he was right but could not say so lest she be forced to tell the rest of her story. "So," he said, "we can assume that something was either generated or present in the mixture at Alamogordo that, in one case, stopped the reaction, in the next case, permitted the thing to work and, in the third case, started the atomic fire in the earth." "How do you go about finding it?" she asked. Virginia was interested. This theory was new to her, but it sounded reasonably solid. He grinned unhappily. "The trouble with making experiments in atomic explosions is that it leaves so little stuff to measure afterwards." He lifted a crystal of the space-resonant elements and looked at it with wrinkled forehead. "Something in this crystal holds the answer. I think we should analyze this material right down to the most infinitesimal trace. Then we can find out which of the included elements is responsible for the original problem." "I can help," said Virginia. He smiled grimly. "Your job is to keep an eye on Maddox and Kingston. See if you can locate their men on Earth One, also see what you can do toward locating those four subcritical masses. We must keep Kingston and the rest of his gang from entering Earth One." He looked at her thoughtfully. "Also keep an eye on your own collection." Virginia smiled and nodded. She looked him squarely in the eye and said, "My collection of those elements is very small."