Quick recap
Catherine, a young woman living with her sister on the La Barre-y-va estate in Normandy, asks Raoul d'Avenac, who is Lupin, for help because she feels threatened. Soon a man dies on the property and Inspector Béchoux joins the case. Behind the deaths lies a treasure hidden by the house's former owner, and clues that only make sense with the local river and tides. Raoul investigates, protects the sisters and tries to work out who in the family is after the gold. The book blends romance, puzzle and the Normandy coast, Leblanc's favorite setting.