When a young man is found dead of an apparent overdose, Dixon fiercely pursues a homicide investigation as an old unsolved case comes back to haunt her. Price and Maroun risk putting a witness in harm's way to expose their suspect.

The murder of an off-duty NYPD detective threatens to tear the city apart; Cosgrove mourns the loss of a friend and asks Capt. Benson for help solving the case; McCoy and Price disagree on how to prosecute the culprit.