War has taken everything from physicist Keizo Kan. His young daughter was killed in the Great Tokyo Air Raid, and now his Japanese American wife, Noriko, has been imprisoned by the brutal Thought Police. An American bomber, downed over Japan on the first day of August 1945, offers the scientist a surprising chance at salvation. The Imperial Army dispatches him to examine an unusual device recovered from the plane’s wreckage—a bomb containing uranium—and tells him that if he can unlock its mysteries, his wife will be released. Working in secrecy under crushing pressure, Kan begins to disassemble the bomb and study its components. One of his assistants falls ill after mishandling the uranium, but his alarming deterioration, and Kan’s own symptoms, are ignored by the commanding officer demanding results. Desperate to stave off Japan’s surrender to the Allies, the army will stop at nothing to harness the weapon’s unimaginable power. They order Kan to prepare the bomb for manual detonation over a target—a suicide mission that will strike a devastating blow against the Americans. Kan is soon confronted with a series of agonizing decisions that will test his courage, his loyalty, and his very humanity.