L'ami de mon fils (1997)

Louise has been a widow for years and teaches literature in a high school. She divides all her time between books and her son, Martin, who still lives with her. During a family lunch, she meets Martin's best friend, Stanislas, a young painter of Russian origin, who is studying at the Beaux-Arts and whose talent promises a brilliant career. Louise is still finding Stanislas very attractive and already the young man is madly in love with her. All it takes is a little something to bring the two lovers together in the same passionate embrace. Informed by his mother, Martin pretends to be delighted by this unexpected rapprochement between the two beings he loves the most. His rage bursts, however, during the family meeting that Louise has organized to make her affair with Stanislas official.