Ship captain Marco (Lindon) is called back to Paris after his brother-in-law commits suicide. He finds his sister Sandra (Bataille) facing bankruptcy, and her teenage daughter in hospital after a sexual assault. Sandra holds businessman Edouard Laporte (Subor) accountable for her family’s downfall. Marco moves into the apartment building where Laporte’s mistress Raphaelle (Mastroianni) and young son live. Unwisely, he begins an affair with Raphaelle while trying to get to the bottom of a sordid, increasingly dangerous mystery.