Detective Montalbano investigates the murder of a local businessman called Lapecora. Lapecora's widow suspects that he was killed by his lover Karima, a young Tunisian woman who mysteriously disappeared on the day of the murder. After succeeding in tracking down Karima's five-year-old son Francois, Montalbano realises that the case might be linked to that of a Tunisian man, also killed in mysterious circumstances on the same day that Lapecora died. Meanwhile, Montalbano's partner Livia, who has been entrusted with looking after Francois, becomes very attached to the young orphaned boy.

When the naked dead body of a young woman is found in a villa outside Vigata, Montalbano discovers that she had recently bought the villa and was in the process of restoring it using her wealthy husband's money. When the case is taken from Montalbano and given to rival inspector Panzacchi from nearby Montelusa, Panzacchi draws some easy conclusions and the investigation risks going badly off course. Will a proud Montalbano stick his neck out to regain control of the case or will he allow his incompetent colleagues to pin the murder on the wrong suspect?