The story takes place during a Sunday in the late summer of 1912. Monsieur Ladmiral is a painter without any real genius and in the twilight of his life. Since the death of his wife, he lives alone with Mercedes, his servant. As every Sunday, he invites Gonzague, his son, a steady young man, who likes order and propriety, accompanied by his wife, Marie-Thérèse and their three children, Emile, Lucien and Mireille. That day, Irène, Gonzague's sister, a young non-conformist, liberated and energetic woman, upsets this peaceful ritual and calls into question her father's artistic choices.