Rick Devon's body is found in a park, and the death is assumed to be drug related. Detectives Cyrus Lupo and Kevin Bernard stumble find a key in a bathroom that could have been left by the killer. Prints on the key lead the detectives to Diego Cardenas, who now works at a home for mentally challenged adults. The detectives discover a relationship between the murdered victim and another resident of the home, Pete Haynes. Rick and Pete's relationship guides the detectives to uncover a secret that could reveal the killer.