World War Two opens with a lie: in 1938, German operatives stage an attack on the Gleiwitz radio station and dress it up as a Polish assault, giving Hitler his pretext to invade. The film traces the deception war that follows on both sides. At Trent Park, captured German generals talk freely in bugged rooms, unaware British intelligence is recording every word. The Ultra codebreaking program stays hidden behind what Churchill called a 'bodyguard of lies,' fed by double agents and fabricated intelligence designed to protect the secret at any cost. Performer Josephine Baker moves through occupied Europe passing messages hidden in sheet music while maintaining her cover as an entertainer. Elsewhere, camouflage units build entire decoy airfields and dummy tank columns to draw German bombers away from real targets. Historians and archival footage move between these episodes, building a case that the war's outcome turned as much on convincing lies as on combat, and that the deceptions worked because both sides took the practice of lying seriously as a discipline.