When Anna Maria Giusti returns from holiday to find her elderly neighbour Constanza Altavilla dead, with blood on the floor near her head, she immediately alerts the police. Commissario Brunetti is called to the scene and it seems the woman has suffered a fatal heart attack. Patta, the Vice-Questore, is eager to dismiss the case as a death from natural causes, but Brunetti believes that there is more to it. It soon transpires that there are some faint bruises around her neck and shoulders, indicating she may have been shaken. Could this have caused a heart attack? Was someone threatening her?

Meanwhile, Brunetti meets Signora Altavilla's son, Niccolini, who tells him that since her retirement she had been helping out at a nearby nursing home. Brunetti visits the home with Ispettore Vianello to try and find any information that might be connected to the case. While they speak to those she spent the most time with, it appears that there is some hostility between the residents which raises Brunetti's suspicions. Once again, he enlists the help of Signorina Elettra, who discovers that Signora Altavilla was involved with an organisation that helped women at risk, providing them with a safe house. Could this have something to do with her death?

As the investigation takes an unexpected twist in events, Brunetti needs to find out the truth before it gets buried within a community that seems to be slipping deeper and deeper into deception and lies.