What if June 6, 1944, marked the date that America dropped an atomic bomb on Germany? A seasoned creator if speculative fiction, Gregory Benford tells the story of Karl Cohen, a Manhattan Project chemist and mathematician who has discovered an alternate solution for creating the uranium isotope needed to cause a chain reaction: U-235. After convincing General Groves of his new method, Cohen works alongside Enrico Fermi, Leo Szilard, and Robert Oppenheimer, preparing to have a nuclear bomb ready to drop by the summer of 1944—but in this alternate history, none can guess how the world will be changed.