Jean Matrac (Humphrey Bogart) is a French journalist who is opposed to the Munich Pact. He is framed for murder and sent to Devil's Island as punishment. He and four other convicts Marius (Peter Lorre), Garou (Helmut Dantine), Petit (George Tobias) and Renault (Phillip Dorn) decide to escape from the island. They board a ship which is bound for Marseilles. In the meanwhile, Ship’s Captain Patain Malo (Victor Francen) hears that France has been defeated in the war and decided to shift the ship to Great Britain. However, a fascist sympathizer Major Duval (Sydney Greenstreet) tries to seize the ship for Vichy.