It's the winter of 1450 and Paris is in a panic. A pack of ravenous wolves is loose in the city, feasting on human flesh. Lorenzo Boccaccio is summoned by a Dominican inquisitor who claims that Lorenzo's business agent is tied to the sorcery behind the wolf attacks. He demands that Lorenzo and his brother Marco help him root out the evil. Rivals in business and love, the brothers make for a reluctant partnership. Even so, they are confident the wolves are a natural phenomenon, not men or demons traveling in wolf form. But events soon prove that the monks and peasants are right. These are no ordinary wolves. And if they are not defeated, the city's filthy alleys will be awash in blood.