Olivia and Elliot go to Peter's apartment and realize he is unreasonably paranoid. They bring him back to the station. Peter tells the detectives that he panicked after he thought that the woman was going to disclose his location. Fin searches Peter's apartment and finds a bloody knife. Ryan, the medical examiner processes the knife and finds that the blood on it matches the victim. Peter's lawyer arrives and tells the detectives that Dale mishandled the evidence and it is inadmissible in court.

Later, Elliot visits Judge Donnelly and asks her if he can help him with the case. During arraignment, Peter's lawyer asks Judge Donnelly to drop the charges because of the mishandled evidence and she agrees. Dale tells Donnelly that she is making a mistake. Donnelly tells Dale that his mistake allowed Peter to walk free. After the trial, Fin and Munch follow Peter to Coney Island. Peter goes on a ride and loses the detectives.

Later, the detectives examine the warehouse and learn Peter escaped through the roof. Elliot and Olivia visit Peter's lawyer and ask her if she knows where Peter is. The lawyer says Peter's parent's were killed and she kept track of him since he was young. The lawyer tells the detectives that Peter had a professor who he sees as a mentor. At the university, the professor tells Olivia and Elliot that Peter painted in his studio. The professor says after 911, Peter became obsessed and less productive. They discover a collage that contains recent newspaper articles about Peter. They bring the collage to the station and see images of what looks like Elliot and Olivia. They receive a call from Peter's lawyer and hear an angry conversation between her and Peter. Elliot and Olivia go to the lawyer's office and see Peter arguing with her. Elliot busts through a makeshift barricade constructed by Peter, then arrests him. Elliot and Olivia put Peter in their car in the garage. The lawyer tells the detectives she will meet them at the station, then gets into her car. She is trapped in her car as it fills with a poisonous gas. Elliot tries to save the lawyer by breaking the glass, but it is too late. Peter screams that his lawyer deserved to die for betraying him.

Later, Elliot finds the word 'guilty' written inside the car. The detectives figure Peter intends to hurt the people who helped the police find him. They bring Gwen and the professor to the station. Gwen gets angry and slaps Fin. Ryan finds a mosquito that recently fed in the lawyer's car. Ryan says before the mosquito died, it fed on the person who set up the trap that killed the lawyer. He says the DNA evidence might be enough to convict Peter. The detectives also find a message that says there will be three more victims.

The detectives go to Judge Donnelly's house after they figure Peter is going after her. Donnelly sits down on a chair and is injected by a syringe hidden in a pillow. The detectives bring the judge to the hospital and the doctors are able to stabilize her. The doctor tells the detectives that the judge was injected by Potassium Chloride. Elliot gets a call and Ryan tells him the DNA test from the mosquito is almost ready. At the lab, the Ryan is stabbed in the chest and killed. Elliot goes to the lab and is ambushed by Dale. Olivia calls the lab. Dale picks up and tells her that Elliot went out for sushi. Elliot wakes up and finds he is taped to a chair. Dale tells him he set Peter up for the Coney Island and lawyer's murders. Dale takes a knife and cuts Elliot across the chest several times. Dale says he is angry at Elliot for humiliating him. Olivia arrives and finds Elliot tied up. Dale pulls a gun on Olivia and tells her she knows too much. Olivia tells Dale she wants to go along with his story. Olivia tells Dale that Elliot has been treating her badly for years and deserves to be in pain. She slaps Elliot several times in the face. Olivia tells Dale that once Elliot is gone, she will need a new partner. Olivia kisses Dale and moves him close to Elliot. Elliot kicks Dale in the genitals and Olivia knocks him out. Olivia frees Elliot and tells him that she knew Dale lied to him when he said that he went out for sushi.