Frank was famous for his expert investigative skills, his unorthodox techniques, and the fact that he was a werewolf. Ryan is human, promoted to detective by Internal Affairs. His first assignment is to investigate Frank's methods. Posing as the werewolf's new partner, wrestling with his own guilt and insecurities as a cop and as a spy, he assists Frank in a murder investigation while simultaneously gathering evidence against him. As Ryan and Frank search for answers, they discover that the governor could be the next target in a string of murders. With the politics of Boston hanging in the balance, the partners must tolerate one another long enough to find the killer before he can strike again.