Saint-Martin-de-Comminges is a small town nestled in the Pyrenees. The kind of place where nothing happens. Until the winter morning when a group of workers discover the headless body of a horse, hanging suspended from a frozen cliff. Toulouse city cop Commandant Servaz can't believe he's been told to investigate the death of an animal. But there's something disturbing about the crime he can't ignore.

Then DNA from one of the most notorious inmates of a nearby asylum is found on the horse's body... and a few days later the first murder takes place.

Madness and revenge are stirring in the snowbound valley, and Servaz must uncover the town's dark secret before the killer strikes again.