In 1941, two years into the Second World War, Werner Heisenberg went to Copenhagen to meet his old friend and mentor, Neils Bohr. At the time, Heisenberg was the head of the German nuclear program. Bohr would later smuggle himself out of occupied Denmark and aid scientists at Los Alamos. Though the actions both take afterward are known, no one knows what was actually said at their meeting in Copenhagen. The fates of nations may have been decided in one evening by the two men, but history will be forever uncertain.