Marseille. 1975. Pierre Michel, a young magistrate who's moved south from Metz with his wife and children, is appointed a judge of organized crime. He decides to attack The Connection, a gangster organization that exports heroin throughout the world. Taking no heed of warnings, Judge Michel sets out alone against Gaëtan Zampa, a emblematic figure of the crime world and a boss whose position and contacts make untouchable. But the judge rapidly comes to realize that, to get results, he must change his methods.