Disgraced knight Crispin Guest has built a new reputation for himself, this time as "The Tracker," a man who can find anything and will do so for a price. But his latest case makes even Crispin wary: he is contracted by Jacob of Provencal, a Jewish physician at the King's court, to find a set of ancient parchments that may be connected to the recent serial murders of several young boys. A demon stalks the streets, putting everyone in danger until Crispin can solve the case.