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.