Stabler is surprised to receive a phone call about a breaking and entering involving a teenage girl. Benson alerts Stabler that she was the one who called him. Stabler wants to know why he should get involved with a case about a teenage girl who was caught taking a shower at a strangers' apartment and Benson has to break the news that when the girl fled, she left behind her clothes and ID and they belonged to Stabler's daughter, Kathleen.
Stabler and Benson later find Kathleen swinging at a playground at Riverside Park. Stabler takes Kathleen home and finds out she took some pills at a party. Stabler wants answers. She swears this was the first time she took drugs and breaks down because she let her father down, again.
Stabler finds out through an undercover informant that his daughter has been taking cocaine and downers as a regular habit. Before he has time to react, Kathy arrives at his work to tell him that Kathleen has run away from home. The informant lets Stabler know of an abandoned drycleaners where Kathleen goes to get high. When they arrive, they find Kathleen partially clothed, unconscious, and in bed with a strange guy. Kathleen is taken to the hospital.
Stabler and Kathy are told that Kathleen shows symptoms of being bipolar: something Stabler wants to hear nothing about. He storms outside to find Benson and Cragen who are there to deliver bad news. The owners of the house that Kathleen broke into earlier issued a complaint claiming Kathleen stole jewelry when she was there. The family also issued the complaint to the DA, and they want Kathleen arrested.
Stabler calls a defense lawyer in for Kathleen and points out what the doctor told him about her mental stability. Kathleen refuses treatment, so the police have no choice but to arrest her for burglary charges. Benson promises Stabler she'll go with Kathleen while she gets booked. Stabler can't help but feel helpless about what's going on.
Stabler continues to have a hard time accepting that Kathleen is bipolar. His wife points out that it's because of his own mother. Stabler heads out to the beach to pay his mother a visit. She is shocked to see her son, since she hasn't had a visit from him in two years. Bernadette becomes upset when she finds out about Kathleen's arrest. She refuses to believe that Kathleen is manic.
Bernadette loses her temper when Stabler suggests she talk to the DA about Kathleen's condition. She still can't believe Stabler's accusations that she, herself, is bipolar... even when Stabler points out several instances in his childhood when she displayed very manic behavior. She accuses Stabler of only contacting her when he needs something from her.
Stabler returns to the couple who are pressing charges against Kathleen. He gives them back a necklace belonging to them that Kathleen stole. Stabler hopes that going to court will help Kathleen realize the severity of her crime.
The defense tries to persuade the judge that Kathleen is not a flight risk. The DA points out that the defendant's own father returned the stolen necklace, owning up to Kathleen's crime. Kathleen flips out in the courtroom and starts shouting that she hates her father. She is carried out by police.
Stabler stays the night at work and that's where Benson finds him. She feels hurt that he never opened up to her about his mother and her condition. She points out that Stabler is the one with the problem because he continues to bottle up all his emotions. He explains to Benson that locking his daughter up in prison was the only option he had to save her life.
Benson meets up with Bernadette for the first time at a restaurant on the beach. Before Benson can talk about Stabler, Bernadette shows her an album of all of Stabler's pictures growing up. Bernadette wanted to prove to Benson that she was a good mom and begins to break down in tears as she talks about Stabler's childhood.
Benson asks Bernadette if she's ever taken medication for her condition and Bernadette recalls only once, when she was married to Stabler's father and he had her committed to a hospital. She talks about how doctors forced medication down her throat and afterwards she felt so empty inside. It was a place she never wanted to go back to again. Benson urges Bernadette to talk to Kathleen.
Bernadette goes to prison to visit her granddaughter. Kathleen is worried that her grandma is only there to chastise her, but instead, Bernadette brings up happy memories she has shared with Kathleen. Kathleen turns angry when Bernadette tries to defend her son's actions that led to her getting arrested.
Bernadette tries to get through to Kathleen. She tells her the story of when she went driving in a snowstorm in 1969 and how at the time, she saw nothing wrong with driving faster and faster because it felt like she was on a sleigh; that is, until she hit a lamppost and totaled the car and broke her son's arm in the accident. Kathleen is shocked to hear her grandma's story.
Bernadette tries to make it clear that Kathleen needs to get help before people start getting hurt. Kathleen admits to sleeping with a lot of boys and later regretting it. Her grandmother tells her that it's in the past and she can start living a fresh new life now, if she can let the people who love her back into her life. Kathleen has to go back to her cell and Bernadette makes Benson promise not to tell Stabler about her visit.
At Kathleen's arraignment, she enters a plea of guilty. As part of a deal with the DA, Kathleen volunteers to enter an in-patient psychiatric care center, a plea that all parties agree on. Kathleen promises the judge that she'll take medication and begin talking to a therapist. Once Kathleen completes her treatment, all charges will be dismissed, which is great news to Kathy.