Série noire(1955)

Léo Fardier is a police inspector who goes to prison undercover as a convict. He shares a cell with Mariani, a Corsican mafioso, whose trust he earns. The day Léo leaves prison, the criminal entrusts him with a letter to deliver to his estranged wife. He finds her, and she falls under his spell. The problem is that he, too, has fallen in love with her.