This week's investigation centers on the victims of the Triple Killer, someone who strangles women with rope and positions them as if they were in a coffin. His previous victims date back four years ago. The most recent victim, Linda Russo, worked for a cable company and had previously identified a man from her office as being suspicious. This man, Paul McCardle, had staked out Linda’s apartment, although his alibi checked out for the night of her murder.
Another victim, Kim Foster, leads the detectives to Marcus Gates, who they arrest after speaking with his former inmate, Jerry Tyson. Jerry agrees to talk with the police for early release and protection until Gates is locked away. Jerry admits that Gates had used partners, helping the detectives to identify McCardle as a ploy in Gates plan. McCardle and Gates lived together in a foster home several years earlier.
Esposito checks in on Jerry’s girlfriend as a favor, who is in the process of being attacked by Gates. He is arrested and admits to the murders of all the victims.
Ryan and Castle head to the hotel that Jerry is staying at to inform him of the arrest of Gates. After some quick conversation, Castle realizes that Jerry is the real Triple Killer. He attacks Ryan and ties Castle up, while holding a gun to him. Martha calls Castle and Jerry warns him not to say anything stupid. Castle tells her he loves her, leading Martha to call Beckett. The detectives show up to the hotel, but Jerry Tyson is already gone.