The series centers on Detective Jack Hale of the San Francisco Police Department's Deviant Crime Unit. Hale has chosen to be on the front line of the city's toughest division after taking a hiatus from the force when his partner -- with whom he had a personal relationship -- died in the line of duty. Intense and private, Hale is haunted by his own personal demons and fights to maintain his sanity and career. While investigating his cases, Hale works closely with his boss, Lieutenant Matt Cavanaugh, who -- despite his better judgment -- supports Hale's unorthodox tactics. Meanwhile, Detective Danielle Carter is preparing to join the force and Hale's world, to go one-on-one with the idea that "behind every monster there's a mystery."