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.

The naked body of a young woman is discovered on a beach near Vigata. The girl was shot in the face, her identity is unknown and the only clue police have to go on is a butterfly tattoo on her shoulder.Montalbano sets to work trying to establish the girl's identity and investigates possible links between the murder victim and a local charity with connections to the church. Meanwhile, his relationship with Livia continues to suffer as a result of his poor work/life balance.