Isère, on the marches of France. A regiment of dragoons enters a seemingly deserted village to find several badly mangled bodies and evidence of an attack by a wild animal. Survivors speak of a massive beast with almost human eyes, of a werewolf... The thing's trail leads over the border with the Duchy of Savoy, and the commander of the dragoons takes a small detachment, in civilian clothes, after it. With them is his cousin: Jean-Baptiste Poulain.