Captain Paul Danceny is arrested next to the corpse of Gabriel Fabian, a doctor. Placed in police custody, he had time to call Marie Jourdan to help him. The latter, from the Lyon PJ, went to the gendarmerie where Paul was questioned by a prosecutor convinced of his guilt. The forensic doctor established that Fabian had been the victim of a road accident. Paul, for his part, admits that he has an alibi: he is the lover of the wife of the director of the clinic. Jourdan and Danceny go to the school to investigate.