A family is making a cruise with its boat on the “Canal du Midi”.When they were crossing a canal lock they discovered the corpse of woman in the water.The police captain Maxime Fabre is in charge of the investigation: when he sees the corpse he recognizes the woman: it’s Sandrine Richomme, spouse of the Parisian judge Richomme.The woman has a bruise on the face and also marks of pressure on the front.On the boat of the Richomme family there is a great disorder.Then Maxime Fabre goes to the house of the mother of the judge: the judge says him that he had a quarrel with his wife and that he walked from the boat till the house of his mother and decided to stay there because his son fell asleep there.Two female students who are travelling also on the canal listened to noises of a quarrel in the boat of the Richomme and when they passed again at 11 pm. , there was light but nobody was on the boat.Maxime Fabre is waiting for the reinforcements and on the boat of the Richomme family he meets the police captain Izia Moreno sent from Paris.