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.
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.
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.
