In rural France during World War II, Lucien Lacombe (Pierre Blaise) is a young man who joins the French Resistance but is rejected due to his youth. Feeling resentful and disillusioned, he aligns himself with the Nazis and becomes part of the Gallic arm of their Gestapo. As he grows in power and influence, Lucien falls for France Horn (Aurore Clément), a beautiful Jewish woman living in hiding with her father and grandmother. Their complicated relationship is set against the backdrop of the war, with Lucien forced to confront his own morality when the Resistance attacks a hotel where French collaborators are being held.