Ex-convict Georges Manda (Serge Reggiani) returns to the free world determined to go straight and takes a steady job as a carpenter. Unable to completely shake his connections with the underground, he meets with a former prison mate, older gangster Félix Leca (Claude Dauphin), who introduces him to his mistress, the sweet but guarded Marie “Casque d’Or” (Simone Signoret). Marie and Georges fall into a passionate relationship, driving Félix to do everything in his power to ruin the couple.