In December 1938, in Berlin, a simple chemical experiment showed for the first time that the atom can be split, releasing immense power. Within months, the Wehrmacht had started research into nuclear weapons. The Germans were the first to start work on the atom bomb. The programme investigates the reasons why Hitler was not the first leader to use it, drawing on new evidence gathered by historian Mark Walker. Dramatised scenes, eyewitness accounts from Allied and German scientists, interviews and archive footage are all employed.