In Les Halles, in the heart of Paris, the long-divorced André Chatelin, an honest and respected man who runs a successful restaurant, is visited by an unknown young woman. She says she is Catherine, the daughter of his ex-wife Gabrielle, who has died leaving her homeless and penniless. André gives her a room and a job, but she soon starts abusing his kindness. She sows discord between André and his young friend Gérard, a medical student who is like a son to him. And she starts stealing money to support her mother, who is not dead but an ex-prostitute who is now a hopeless drug addict in a sordid hotel.