When a wealthy Venetian woman is found brutally murdered, the prime suspect is her Romanian maid, who has fled the city. As she attempts to leave the country, carrying a considerable sum of money and forged papers, the maid runs into the path of an oncoming train and is killed. Case closed.

But when the old woman's neighbour returns from abroad, it becomes clear that the maid could not have been the killer. Commissario Brunetti decides - unofficially - to take the case on himself.

As Brunetti investigates, it becomes clear that the motive for the murder was unlikely to have been greed, rather that it had its roots in the temptations of lust. But perhaps Brunetti is thinking of the wrong deadly sin altogether...