In a little town in the south-west of France during the German occupation, Édouard Martin handles the insurance needs of his fellow citizens and also, unknown to his family, is the local head of the Resistance.

An officer in the First World War, he runs his network on disciplined lines, following orders from headquarters in London, who supply radios and arms by air.

When a stranger named Jourdan is parachuted in and wants to mount dangerous attacks, he deduces that the man is an imposter and has him shot.

Lancaster bombers flatten the factory and the Germans, deducing that Édouard must have known in advance, arrest him.

Damaged but alive, he is rescued by his network and, when the Germans retreat in 1944, reunited with his proud family.