Casey is taken off the streets where she's been working as an undercover hooker and finds herself reassigned to the Second Precinct, effective immediately. She meets her new partner, Jason Walsh (Jeremy Renner), whose last partner, Detective Burt Kowalski, was just murdered. Tasked with tracking down the murderer, Walsh races off to investigate Kowalski's past, with Shraeger trailing behind.
As the duo seeks out the cop killer, the secrets and eccentricities of the rest of the department begin to emerge: Prank-magnet and social climber Detective Eddie Alvarez (Kai Lennox) has no qualms about stealing cases, as long as he can turn them into front-page stories that make him look good; Detective Eric Delahoy (Adam Goldberg) is trying to get himself killed in the line of duty for reasons known only to him and his doctor; his partner, Leo Banks (Harold Perrineau), is convinced he is going to die and refuses to take off his bulletproof vest; and the very religious Detective Henry Cole (Josh Close) is trying to keep his unholy past from both his streetwise partner, Alison Beaumont (Monique Gabriela Curnen), and from his boss, Sgt. Brown (Terry Kinney), who is struggling to rid the Second Precinct of corruption.
