Autumn 1941. The war is going badly for Britain and its allies. If Hitler is to be stopped, a new weapon is desperately needed. In Cambridge, professor Tom Wilde is approached by an American intelligence officer who claims to know of such a weapon - one so secret even Hitler himself isn't aware of its existence. If Wilde can smuggle the package out of Germany, the Third Reich will surely fall. But it is only when he is deep behind enemy lines that Wilde discovers why the Nazis are so desperate to prevent the 'package' falling into Allied hands. And as ruthless killers hunt him through Europe, a treacherous question hangs over the mission: if Hitler's secret will win them the war, why is Wilde convinced it must remain hidden?