La demoiselle d'honneur (The Bridesmaid)

Christine has brought up alone her three children Philippe, Sophie and Patricia. She introduces them to her future companion Gérard, but the romance comes to a sudden end and Gérard moves out quickly. At Sophie's wedding, Philippe falls in love with one of the bridesmaids, Senta, who sees in him the love of her life. Philippe discovers very quickly Senta's excessive sentimentality and her mythomania. But as he is madly in love with her, he treats her excesses in a light-hearted way, even when she asks him to murder someone to prove his love. He plays along with her, by pretending that he has killed the tramp whom she hated. When she in turns boasts that she has killed Gérard with a glass dagger, he checks that his mother's former companion is well and truly alive. But when he is summonsed to the police station about a theft committed by his sister Patricia, he learns that one of Gérard's relatives has been stabbed ... Discovering in a cupboard in Senta's flat the body of a girl whose disappearance had been announced on TV, Philippe becomes aware of the murderous folly of Senta.