In a small Sicilian town, the head of the criminal investigation department, Marineo, is murdered. It appears to be a Mafia crime. On the same day, another death is reported: the Marchesa Pecchi Sciolya commits suicide. Corrado Cattani, an experienced police officer, is appointed to replace the murdered commissioner and moves to Sicily with his wife and daughter. While investigating the murder, Corrado meets Titti Pecchi Sciolya, a drug-addicted woman, and gradually falls in love with her. He soon discovers a hidden connection between the murder of Marineo and the suicide of the Marchesa.