Inspector Montalbano is puzzled by the kidnapping of Susanna Mistretta, a young woman whose once-wealthy family has fallen on hard times. When the kidnappers contact the family to demand a ransom, the responsibility of coming up with the money falls on an estranged relative. But something in the case just doesn't add up.

The death of local construction magnate Girolamo Cascio leads Montalbano back to the murder of Cascio's leading competitor, Giacomo Aletto, who was shot and killed two decades earlier. Rocco Pennisi, Aletto's partner, was sent to prison for the crime. But was the right man convicted?

Inspector Montalbano discovers the existence of a secret underground dwelling beneath Mimi's family home and finds a trunk containing the dead body of a young woman who had disappeared six years earlier. As he begins his investigation, Montalbano makes the acquaintance of the victim's alluring twin sister.