Pierre Rossi and Béatrice live in the same block of flats in Marseille and love each other. One night, Béatrice leaves her apartment. Pierre knows that his fiancée goes to a rendezvous, but she would not tell him more than just that. Worried, Pierre follows her but he is attacked and stolen his identity papers by two men, Tom and Nasol, on the payroll of Quaglio, one of the city's bosses. Later on...