Zach Adams is one of the best detectives in the country. Nicknamed Cowboy, he's a soft-spoken homicide detective known for his integrity and courage under fire. He serves on a federal task force that has a single mission: to hunt down Dominic Abend, a European gangster who has taken over the American underworld.
In a centuries-old forest under a full moon, a beast assaults Zach, cursing him forever. In the aftermath, he is transformed into something horrible—something deadly.
Now, the good cop has innocent blood on his hands. He has killed—and will kill again—in the form of a beast who can't be controlled or stopped. Before he can free himself, he's going to have to solve the greatest mystery of all: How can you defeat evil when the evil is inside you?