While on a cruise on the Canal du Midi,a family discovers the body of a woman during the passage of a lock in Marseillette. Captain Maxime Fabre was sent to the scene. He discovers the identity of the victim: she is the wife of a Parisian magistrate. A delicate investigation is looming. Too delicate for the provincial policeman who finds himself forced to team up with Captain Izia Moreno, who disembarked from Paris.