A criminal turned state witness informs Montalbano of an arms stash in a cave just outside Vigata. Also uncovered in the cave is a secret chamber where the bodies of two lovers, killed sometime in the 1940s, were buried in a bizarre ritual. An intrigued Montalbano must challenge the Mafia and deal with the arms cache before he can investigate this second find.

Mr Luparello, a renowned local engineer and leading political figure, is found dead in a car at a notorious prostitution spot on the outskirts of Vigata. The coroner rules that he died of a heart attack following an amorous encounter. Fending off pressure from prominent ecclesiastical figures who wish to keep the case under wraps and navigating the intricacies of local party politics, Montalbano goes about making sense of the available evidence, including the incongruous discovery of an expensive necklace found at the site of the murder.