Since the day their mother Aline remarried, Patrice and Eric, a joyful pair of twins, have been very happy. Indeed, François Chantour, their stepfather, is very kind and behaves like a big brother to them. Even if they are not very rich, the four of them live a cheerful life in their charming house. The trouble is that, in Lyon, the family on the boys'father's side are worried, especially the twins' grandmother, who fears Patrice and Eric are given a bad education. She therefore brings them to her big house in the hope of their improving their manners. A very unfortunate decision indeed.

On this beautiful May 1st, Thérèse is about to give birth. Their presence at home is undesirable, so Jean, her husband, decides to take François, their little boy, to a soccer match. Their plans change when they meet a former factory mate who seems to have made a success of his life. This man, Blanchot, decides to return to Jean a sum of money he had once borrowed. Trusted, Jean is drawn into a clandestine circle, where his apparent luck delivers him without ulterior motive to Blanchot, who is one of the ringleaders. The police interrupt the dangerous game, putting Jean, who has no identity papers, in an awkward situation.

Bob, a talented draftsman, and his young wife Marie-Blanche, a young antique dealer, adore their only son Gégé. But for the most trivial of pretexts, the couple often quarrel. A more serious quarrel leads to separation and divorce proceedings. Gégé spends a week with one of them, and a week with the other, each vying with the other for the little one's affection. But Gégé realizes that he can perhaps initiate a reconciliation.