Zach Adams is one of the best detectives in the country. Nicknamed Cowboy, he serves on a federal task force that has a single mission: to hunt down Dominic Abend, a European gangster. After a brutal murder gives them a lead, Zach feels like he's finally on Abend's trail. But things get complicated and very, very weird. Zach is beginning to suspect that Abend's evil goes beyond crime - perhaps to the edge of the supernatural. In a centuries-old forest under a full moon, a beast assaults him, cursing him forever. In the aftermath, Zach is transformed into something horrible - something deadly. Now, the good cop has innocent blood on his hands. He has killed - and he will kill again - in the form of a beast who can't be controlled or stopped.