Saul Stein

Evidence from the case of a young woman who was shot to death confirms the Chicago P.D. has a serial killer on its hands; Voight welcomes Kenny Rixton to the team when Ruzek takes another assignment.

Lindsay's mother, Bunny, becomes a murder suspect when her boyfriend is shot; high school students overdose on drugs; Lindsay finds herself up against the review board.

Olinsky goes under cover as a hit man for hire after Lindsay is tipped off about a grieving father looking to avenge his daughter's death; when Ruzek returns from his undercover assignment, Voight puts him on patrol duty.

Frasier hunts for a schoolmate who was expelled for the Crane boys' prank.

Benson investigates a police officer's accusations of sexual assault; Capt. Tucker's retirement party ends in tragedy.