The yacht of a wealthy woman docks at Vigata's harbour as a disfigured body is discovered at sea. Coastguard Laura Belladonna is assigned to the case to assist Montalbano and the two soon become close. The investigation casts doubts on the motives and sincerity of the yacht's crew and Montalbano begins to suspect that there may be more to the story they have given him.

An elderly couple, both religious fanatics, barricade themselves in their home and begin shooting from the windows for no apparent reason, until Montalbano's men finally succeed in disarming them.

There seems to be no justification for the couple's insane actions, but police find a strangely disfigured inflatable doll inside their home. A few days later, an identical doll is discovered in a rubbish bin and Montalbano has a bad premonition.

Soon enough, a series of strange occurrences develops - disquieting letters bearing riddles are delivered to Montalbano at Vigata police station, while a young woman is reported missing. A disturbed maniac is playing a macabre game of treasure hunt with the inspector and the riddle must be solved before it's too late.

Fazio is missing. He's not at home, his mobile is switched off and his father is worried. Believing that the young officer had been working a secret investigation on his own, Montalbano fears that Fazio may be in serious trouble and a frantic search is mounted in an effort to find him alive.

As torrential rain pours down on Vigata, a plastic bag containing a body cut into pieces is found in a clay field. All the signs point to an old-fashioned Mafia killing. But why is Montalbano's trusted colleague and friend Mimi Augello suddenly irritable and short-tempered, and why is he insisting that the investigation be assigned to him? Could Mimi somehow be involved in the case?