In Vichy Paris during World War II, career criminal Jean Picard [Errol Flynn] awaits execution. French Sûreté inspector Marcel Bonet [Paul Lukas] has pursued Picard for 15 years, finally apprehending him for murder.
An air raid hits the prison just as Picard is about to be guillotined, and he escapes to the apartment of his best friend, Henri Duval [Sheldon Leonard], demanding forged papers and 5,000 francs. While Duval is away, Picard seduces his willing girlfriend Louise [Faye Emerson], and in a cruel turn of fate, Duval betrays Picard to the Sûreté.
Bonet captures Picard in Bordeaux, and their return to Paris is interrupted by a bridge blown up the night before, a sabotage that delays them as a German troop train passes. The Germans round up 100 Frenchmen to be executed in five days unless the saboteur is found. Picard, convinced he may still slither free, offers to surrender himself, already condemned to death, and Bonet—at once skeptical and pragmatic—agrees to stage a capture that will fool the Nazis into believing Picard is the real culprit.
Picard, now going by the alias Jean Emil Dupont, slips into a shop and is instantly drawn to the woman behind the counter, Marianne [Jean Sullivan]. Marianne is a ward of the shop’s owner, Mme. Maret [Lucile Watson], whose own son is among the hostages. With only three days left before the executions, Picard plays the dutiful captive while Bonet plays along, even as Mme. Maret searches for a fall person to trade to the Germans in exchange for her son’s safety. Her first candidate, Brenoir, proves to be too cowardly.
To clear the path for a wider escape, Bonet fabricates a story of having shot Picard when he tried to flee, with Picard’s supposed body lost in a river. Yet the evidence gathered by local gendarmes points to three saboteurs, and a captured suspect is brought to Bonet’s hotel room. Thinking fast, Dupont reveals Bonet’s real identity, giving Bonet a chance to claim that both he and the captured man are undercover Sûreté operatives cooperating to ensnare the fugitive. The plan works: the suspect is released, and the pair discovers the fugitive to be Major Andre Varenne of the Free French Army, whom they aid in his air evacuation to England.
The next morning, Dupont leaves Bonet behind as he plans to rendezvous with Marianne after Sunday mass, imagining a picnic as a pretext to find an unguarded escape route from town. Meanwhile, the local priest, Father Le Clerc [Dennis Hoey], uncovers a second Maret plot to frame three local men for Dupont’s supposed crimes, a plan he denounces as murder.
As Bonet’s health falters, Dupont claims he will have the priest hear his confession before venturing out again. Marianne helps him slip past a mob stirred up by Mme. Maret, while Father Le Clerc again suppresses the crowd. Dupont announces he will head for Paris, and Marianne accompanies him, hoping for a fresh start in Martinique.
Back in Paris, Bonet grows desperate and decides to surrender as the saboteur. Then Jean returns, ready to do the same, asking only that Bonet retrieve Marianne from her vigil. Jean convinces the Nazis he was the sole saboteur. When Bonet goes to Marianne, she asks him, “What is he really like, deep in his heart?” Bonet pauses, then answers, “He was a Frenchman.”
> What is he really like, deep in his heart?
> He was a Frenchman.
