The episode begins at a psychiatric institution where the nurse is on her rounds. She learns that a patient named Rene Caldwell, is missing. Later, she finds Rene’s dead body in the shower. The team arrives at the crime scene. Officer Riley tells Tommy and Megan that Rene’s roommate, Coleen, told them that Rene did not come back to the room after dinner. She also tells them that the nurse found the body during the 10 pm bed-check. Riley flirts a little with Tommy and leaves. Megan suspects that something is going on between them, but Tommy tells Megan that he is saving himself for someone special. Megan examines the body and declares that the girl has been dead for 12 hours.
Tommy tells Megan that when he arrived at the scene, the heat was turned up to the max on all the showers. He feels that all that heat could have accelerated the rigor mortis. Megan is impressed. Megan also feels that the killer was smart enough to strike Rene in the shower and have all the evidence washed off. She notices three blows to the head with some blunt object. The duo meets the Ward Director, Derrick Malcolm. Malcolm tells them that although Rene was a paranoid schizophrenic, she was a strong girl. She was committed to getting out of there and moving on with her life. Director Malcom tells them that there was no security breach. Megan says that it could be the work of some patient or an employee. They decide to talk to the girls.
Malcolm insists that he be present during the interviews, but Tommy says that he cannot allow it. Malcolm does not allow the interviews and asks them to get a court order. They are left with no options and they let Malcolm be present during the interviews. The interviews don’t seem to be of any help. On their way out, a patient named Darby intentionally runs into Megan. She hands her a note asking Megan to meet her behind the cafeteria. They meet Darby and Darby tells them that she is not crazy. She says that the previous night she saw a man climbing down the heating vent in the hallway right outside her room. She tells them that the man came to kill her because of what she knows, but accidentally killed Rene. Before she could tell them any further, an attendant arrives and takes Darby away.
Tommy tells Megan that he will have CSU process the vent. At home, Megan tells Joan about the partial print found on her father’s suicide note. She wants Joan to sign on the exhumation papers, so that she can process the body and find out the truth. Joan refuses to sign. At the center, Megan meets Stafford and tells him that she needs his help in getting an exhumation order. Stafford tells her that he will see what he can do. Later, Megan examines Rene’s wounds and they figure out that the murder weapon is a ball-peen hammer. They find some trace material on Rene’s shoulder that seems like petroleum jelly. That is why the shower could not wash it away.
Tommy calls and tells Megan that Darby’s sister, Beth, was killed two years ago. He says that the lead detective on Beth’s case is coming over to the precinct to brief them. They meet Detective Mo Childs, who tells them that Julia Stone, the mother, raised her children after her husband’s death. On the night in question, Julia put Beth to bed early so that she could watch television with Darby. An hour later, they heard Beth’s screams and they rushed to the room. Both of them saw a male fleeing through the window. Beth was killed from exsanguinations due to multiple stab wounds. Childs believes that the killer spotted Beth in one of the beauty pageants she took part in. He feels that these pageants are magnets for pedophiles.
Childs wants Tommy to keep him in the loop. Megan and Tommy decide to interview Darby. Once again, Malcolm tries to stop them. He tells them that Darby always lies. Two days back, Darby wanted to avoid an AA meeting, so she went to the infirmary to get something for her backache. Megan figures out that Malcolm is hiding something. It turns out that Malcolm gave Darby a mild sedative. Tommy tells Malcolm that they will be back with a court order. A CSU officer tells Tommy that someone did climb down the vent. And says that they found some sticky substance on the vent. Megan tells Tommy that a similar substance was found on Rene.
All this confirms Darby’s story. The next day, they meet Darby. Darby tells them that it is her mother who is trying to kill her. She tells them that she witnessed her mother killing Beth. Julia threatened Darby with Child Services and made her lie to the cops. Darby says that one day Julia caught her trying to call the cops and that is why she locked her up in the mental institution. She adds that Malcolm knows that she is not crazy, and that her mother pays him to see that she doesn’t talk. Tommy tells Megan that the story is too elaborate and he doesn’t trust Darby. He says that they will have to confirm the financial transactions between Julia and Malcolm before they can question Julia. Later, they question Julia.
Julia tells them that Darby is really sick and she is simply making up stories. She always does that to people who try to help her. Julia tells them that she did not kill Beth and also that she did not want to get rid of Darby. She admits that she makes large donations to the hospital because she believes in Dr. Malcolm. She states that is why she has consented to the electroconvulsive therapy. Megan is stunned. She confronts Malcolm and tries to stop him from putting Darby through ECT. Malcolm doesn’t listen and tells them to get an official letter. Later, a sedated Darby is brought into the room and Malcolm prepares for the shock therapy. It is seen that Darby is not really sedated, she spits out the pill from her mouth, attacks Malcolm, and escapes.
Kate tells Megan that Malcolm filed a case against the center. She is angry. Megan gets a call from Lacey and Lacey tells her that Darby has come to their apartment. Tommy and Megan rush to Megan’s apartment. Megan is glad to see that the girls are fine. Tommy tells Darby that he will take her to the station. Megan thanks him for not sending Darby back to the institution. At the station, Tommy tells Darby to narrate the incident that happened on the night in question. Darby tells them that her mother put Beth to bed early, but Beth didn’t want to sleep and she kept screaming. Her mother went up three times to calm Beth.
The third time her mother did not come back, so Darby went to check. She says she found her mother sitting next to Beth, with a bloodied knife in her hand. She tells them that Julia destroyed the clothes and the murder weapon. Tommy wants Darby to describe what Julia was wearing. Darby tells him that her mother was wearing grey slacks, grey sweater and a pearl necklace. She says that Julia got rid of the clothes, but probably not the necklace. Megan goes to Julia’s house with a warrant and retrieves the necklace. They find Beth’s blood ‘inside’ the pearls. They bring in Julia. Julia admits that she did destroy the clothes, but she did not kill Beth. She says that Darby killed Beth. When she saw what Darby had done, she didn’t think and quickly got rid of the evidence.
That is how Beth’s blood got into the necklace. She says that she lied to protect Darby because Darby is the only thing she had left in her life. Megan and Tommy don’t believe her. The next day, Curtis tells Tommy that Megan is on her way to the outhouse with Darby. Ethan arrives and tells him that the sticky substance found on both Rene and the vent, is an ibuprofen gel, which is used for muscle pain. Tommy remembers that Darby had gone to the infirmary to get something for her backache. This means that Darby killed Rene. Tommy calls Megan and tells her about the latest development. He tells Megan not to react.
Darby figures out that Megan is lying and she jumps out of the car. Megan chases her and manages to grab her. At the precinct, Tommy tells Darby that they found the murder weapon with her skin cells on it. Darby admits to her crimes, but she says she doesn’t feel guilty for what she did. Case Closed. Later, Megan tells Tommy that she feels terrible that she was wrong about Darby. Tommy tells her that she is human, and it is not possible for her to be right every time.
Megan now begins to doubt that she might be wrong about her father as well. She thinks she is being cruel to her mother. Tommy tries to console her. She tells Tommy that she had a talk with Riley, and Riley told her about their date. Tommy tells her that they only went to a hockey game and that there is nothing more to it. Megan tells him that they should leave the past behind them. She says that he should move forward. Tommy leaves. The episode ends.