Louis Bertain is the owner of a Paris garage which is the front for a robbery gang. He and his accomplices are careful to keep up a civic veneer by day, indulging in criminal activities only when "the red light is on" at night. This status quo is upset when one of the gang members becomes convinced that Louis' younger brother is a police informer.

Gervais escapes from a German concentration camp and assumes the identity of a recently deceased fellow prisoner. Knowing that the dead man has been carrying on a romance by correspondence with Hélène, whom he has never seen, Gervais makes the acquaintance of the woman and they move in, but her sister Agnès dabbles in the black arts, which should be warning enough for Gervais to make himself scarce. Yet he sticks around, intrigued that the dead man's sister, Julia, refuses to blow the whistle on him.

Raven, a mobster just released from prison, settles the score by murdering Mendetta and her partner, who had turned him in. Having taken over Mendetta's various bars, he finds himself at war with other mobsters who want to kill him.

Yves Tréguier, a young orphan, escapes from a reform school in Brittany to join "Dédé la Glace" in Paris, an old-timer with whom he has a sincere friendship. The love of Zette, a young girl he has met, and the benevolent friendship of Father Blain, the bistro owner, give him the desire for regular work. "Jo le Grec", a pimp jealous of Dédé's friendship with Yves, seduces Wanda, a prostitute he loves, and shoots Dédé dead. Blain prevents him from doing the same to Yves, and shoots him in turn. Yves can live an honest life with Zette and the baby she's expecting.

Struggling actor Simon witnesses a murder; he didn't see the killer, but that doesn't stop him from claiming that he did in order to get his name into the papers. Sure enough, the murderer targets him as his next victim. Our hero is temporarily rescued by Jeanne, a fellow aspiring actress who has always had a crush on him.

Henri, the Man from Nantes, comes back to his country after a successful stay in the United States, where he was working for Liski, the drug dealer. With the fame of being a tough guy preceding him, he sets himself to the task of knowing why the French operations were not so profitable - and soon he is master of all links of the organization. He can now get it honed to perfection - or destroy it. Only... the Police are following his every step.

After resolving to start a new life with his girlfriend Jacqueline, Bastien Sassey decides to give up working as a courier for drugs traffickers. So that he and Jacqueline can make a fresh start he agrees to take on one more job for a large sum of cash, but he betrays his employer.