Marseille, 1975. Young investigating magistrate Pierre Michel has just come from Metz with his wife and children, and has been assigned to deal with organised crime.

He decides to tackle the French Connection, a mafia organisation that exports heroin around the world. He refuses to listen to reason and embarks on a personal crusade against Gaëtan Zampa, an iconic underworld figure and apparently untouchable godfather. But he soon realises that if he wants results, he is going to have to change his methods.