A solid historical mystery featuring Niccolo Machiavelli, Leonardo da Vinci, and Cesare Borgia (aka Duke Valentino). The story begins with a section narrated by Damiata, the mistress of Pope Alexander's beloved son Juan, the Duke of Gandia, who was murdered five years prior to the start of the novel. Damiata is brought in by Alexander to investigate Juan's murder because an amulet that belonged to him turned up on a mutilated corpse in Imola, where his other son, Valentino, is in negotiations with the powerful Orsini and Vitelli families. Alexander takes her son, Giovanni (Juan's son), hostage, and tells her to find out who killed his favorite son. Damiata travels to Imola with her companion Camilla, where they lodge in the same palazzo as Machiavelli, who is there as an observer for the republic of Florence. More mutilated body parts turn up, and Damiata and Niccolo follow Leonardo da Vinci as he investigates the pattern in which those parts have been arranged. Damiata and Machiavelli each interact individually with Valentino, who appears to be in a weakened position vis-a-vis the other warlords.I'll suspend my summary at this point, because things get a bit convoluted. Not in a totally overwhelming way, but enough that I would make a mess of it if I tried to describe it all.I will observe that, contrary to the summary offered by the publisher, Leonardo da Vinci is NOT a major character. He's an interesting character, certainly, but he is a secondary character, and anyone who comes to this book looking for "Leonardo investigates" will be disappointed by his extended disappearances.All in all, this was an entertaining page-turner, and I look forward to the next Borgia fiction that I have waiting on my shelf.