A pair of teenager girls race down the street as they play an interactive video game. One of them trips on a duffel bag sitting in front of a church. Curious, they unzip it, only to discover a small human hand. Later, Benson and Fin survey the crime scene. Fin tells Benson that the victim has to be Marnie, a little girl who had been reported missing the prior day. Warner can't pinpoint the time of death because of the cold weather. Benson compares a photo of little Marnie to the dead girl. Sadly, it's a match. Fin stops Marnie's hysterical mother, Susan, from approaching the body. Benson watches, there's nothing anyone can do for her.
Benson releases the details of the crime at a press conference. Ten-year-old Marnie Foster disappeared on her way home from school the previous day and her remains were just found. Afterward, she and Fin discuss the lack of evidence at the crime scene. Fin thinks someone had to have seen who dropped the duffel on the street. Stabler approaches news that the Parks Department has a camera with a bird's eye view of the church. They sent him the video. As Benson takes a call, Stabler pulls up the footage on his phone. He and Fin see the duffel at 2:04 p.m., then run the video backward. There was no duffel at 12:48 p.m., but during the window of time when the duffel was dropped off, a large truck blocked the camera's view. Fin will track down the truck's drivers to check if anyone saw who dumped the body. Benson returns, tells Stabler that Warner wants them at the morgue.
At the morgue, Warner tells Benson and Stabler that Marnie was raped, but no DNA was found. Warner thinks the rapist used some kind of smooth foreign object. Marnie died by suffocation. From behind them, Dr. Cap Jackson reveals that Marnie was suffocated with the pillow that was in the duffel. Cap is covering for Dr. Huang, who's in Washington. He says that the perp made sure Marnie was resting comfortably before abandoning her. He also left her with a blonde doll. Warner adds that the rapist didn't want Marnie to feel pain, as her stomach was full of milk and Zolpidem - sleeping pills. Benson comments that dropping Marnie off at the church was likely the perp's way of atoning for his crime. Cap thinks that given how the perp "showered his victim with love," he may murdered out of fear of getting caught. The next step is rounding up the "usual suspects" of sex offenders.
Benson, Stabler and Fin question a variety of sex offenders. They all have alibis and are dead ends. Stabler and Fin share what they've discovered about the doll with Cap. The doll's name is "Perfect Penny" and she hasn't been manufactured since 1989. Marnie's mother let them know that it didn't belong to Marnie. Marnie's father is on his way back from a business trip. He's been out of town since before Marnie disappeared. Cap offers that most pedophiles work in pairs, so the father still may have abused Marnie. Fin suggests they go welcome Marnie's dad home.
Outside the Foster home, Benson and Fin find Susan arguing with a man they think is Marnie's father. When it turns physical, they approach. The man is Chet Hadler, not Susan's husband, but her lover. Fin questions Chet at the precinct. Chet claims he never touched Marnie. Susan backs that up. Susan says she told her husband about the affair two months ago and told Chet they had to stop seeing each other, but Chet wouldn't take no for an answer. Benson wonders if Chet told Susan about his police record. He forcibly touched a thirteen-year-old girl, his last girlfriend's kid, and wanted a threesome with them. Benson asks Susan if Chet tried that with her and Marnie. Susan is incensed that she would ask that, but Benson points out that Susan lied about where she was when Marnie disappeared. Ashamed, Susan admits that she was at a hotel with Chet when Marnie disappeared.
Later, Benson reports to Stabler that Susan's story checks out and the hotel is sending her a copy of the bill. She also shares that Fin interviewed Marnie's father when he got home and he's in shock, so there's no way he had anything to do with the crime. Cap suggests that the perpetrator may be a woman. A woman who kills and rapes is rare, but not unheard of. Cap goes through all the details of the case so far to convince Benson and Stabler, but they're still skeptical. There have been only a handful of female-on-female molesters in all their years at SVU. And none that have sodomized and murdered a girl. But Cap persists. He thinks the motive in leaving Marnie's body in front of the church wasn't to atone for the sin, but to leave Marnie safe in God's hands. Cap is convinced that the killer is a woman.
Benson and Cap take a coffee break. Benson offers her condolences for the passing of Cap's daughter, asks if he has any plans to reopen his clinic. Cap explains that he's lost his peers' respect for violating patient confidentiality. Benson reminds him that he saved his patients from a killer. When Cap challenges her, Benson admits that she's having a hard time with his theory that the killer is a woman because she's never encountered such a perp. Cap has seen two such women, both of whom were sociopaths. But Cap thinks their killer is different, because of the tenderness with which Marnie was treated. Benson guesses that their perp was abused herself. Cap thinks that the "Perfect Penny" doll is the key to her psyche. It's a totem for the innocence stolen by her own abuser. Benson declares that they have to talk to everyone in Marnie's life.
Benson interviews the Foster's housekeeper/nanny, Rosita, who was away visiting her mother when Marnie was killed. Rosita shares that Marnie had piano lessons on Monday afternoons. That leads Benson to visit Marnie's piano teacher, June Frye. June taught Marnie every Monday for almost two years. But not this past Monday. June says that Marnie's mother called and canceled. June is visibly upset by the loss of Marnie, sharing with Benson that Marnie used to like poking around all the old stuff in her house. June mentions that her parents died in a car accident when she was seventeen and she hasn't changed anything since.
Cap interviews Marnie's gym teacher, Casey, who talks about how much everyone loved Marnie. Stabler gets the same story from Marnie's female teachers, all of whom had alibis for when she disappeared. Cap believes Marnie's killer may surface at her funeral, because she may be mourning Marnie's loss as much as, if not more than, anyone. At the funeral the following day, Stabler, Cap, Fin and Benson stake out positions. No one sees anything unusual until Benson notices a woman bolting. It's June, Marnie's piano teacher. Benson suggests that they talk, but June's not interested.
Back at the precinct, Stabler goes over June's background. She has no record and has never been married. Fin points out that the brownstone where she teaches piano is around the corner from the church Marnie was found in front of. Benson interrupts to tell them that Marnie's mom told her that she didn't cancel the piano lesson. It was June who called Susan to cancel the lesson. In addition, June's phone records show that she canceled a number of other lessons that afternoon. Cap wonders why Marnie still showed up at her lesson if it was canceled. Benson explains that Susan called the secretary at Marnie's school, but she forgot to give Marnie the message. Stabler thinks that June's brownstone is the crime scene. Instead of getting a search warrant, Cap suggests that they just ask June if they can look around.
Benson, Stabler and Cap head to June's house. June is reluctant to talk to them, but Cap smooth-talks their way in. Cap asks June for some tea and Stabler asks to use the bathroom so that they can each take a look around. Stabler tells Cap that anything they can see without opening a door or drawer is fair game. Benson keeps her eye on June in the kitchen. Cap finds a clipping of doll's hair on some sheet music. Stabler and Cap head downstairs, where they find the same kind of pillows that were in the duffel with Marnie. They smell bleach, which indicates that someone was trying to clean up. Stabler notices that the garbage has been taken out to the street. They look through it and find a piece of luggage that's part of the same set as the duffel bag that Marnie was found in. Just then, they hear Benson over the radio calling for an ambulance - June is in cardiac arrest.
Stabler and Cap rush inside June's brownstone. Benson tells them that June collapsed while playing piano. Cap administers CPR while Benson and Stabler find an empty bottle of Zolpidem. Benson shares that June told her to tell Marnie's parents that she's sorry.
Benson, Stabler and Cap visit June at the hospital. Cap encourages June to talk to them, tells her she'd feel better if she did. Benson rattles off the mounting evidence against June - the suitcase in which they found a wooden spoon, the sleeping pills that were the same ones found inside Marnie's stomach and the hair that matches the doll that was left with Marnie. Cap wants to know why June said she was sorry. June says she'll die before she talks about Marnie. Fin reports that there was no DNA evidence on either the suitcase or the spoon. Marnie's prints were found upstairs in the house, but likely along with many of June's other piano students. Benson is convinced it has to be June. But none of the evidence is enough without a confession. Stabler and Benson turn to Cap - he sweet-talked June once, it's worth another shot.
Cap brings the doll into an interview room where June sits. June wishes Cap had let her die and insists that she won't talk. June doesnâ€™t think she deserves to live. Cap switches gears, asks June when she started playing the piano. June says she was five. Her mother taught her, told June it was the one thing in her life where she could find perfection. June says she was an only child. Cap picks up the doll, asks if her mother gave it to her. June says her father did, but she doesn't want to talk about him. June wonders if she should ask for a lawyer. Cap tries to discourage her, which earns him a swift bang on the window.Cap steps out. Stabler instructs Cap that he cannot tell June that she doesn't need a lawyer, because then any confession she makes won't be admissible in court. Cap asks if June can legally change her mind. Stabler says that she can.
Cap returns to the interview room, tells June that they've got to stop talking. Cap takes the doll and says he has to go because June asked for a lawyer. June doesn't want him to leave. She asks if he can stay if she says she doesn't need a lawyer. They resume talking. Cap shares his own family history with June to try to get her to talk. June finally opens up and shares a story of her father's sexual abuse of her when she was seven, how he called her his "perfect little doll." Cap suggests that June gave Marnie the doll to keep her safe. June talks to the photo of Marnie, wondering why she came to her house when June told her mother not to send her. June describes how she gave Marnie the milk with the sleeping pills, then used the spoon. Then she confesses how she wrapped Marnie in the sheets with the pillow and doll and left her at the church.
As Benson, Stabler and Fin describe to Cap what will happen next for June, she kneels down in the next room to say a prayer. She asks for forgiveness and comfort for Marnie's soul and the souls of others who needed her comfort and protection. Cap guesses that talking about Marnie's murder may have triggered more memories. Stabler suggests that they interview June's other students as well as her neighbors. June's students have mostly good things to say about her. But one, a fifteen-year-old named Becca, has a strange story. She says that June blew her off on Monday. Becca was walking down the sidewalk and came upon June arguing with an old lady. Becca said hello, but June ignored her. June and the old lady went into June's house and Becca left.
Benson reports to Stabler and Cap that the old lady is June's mother, Elaine Frye Cavanaugh. It turns out that June's father died when she was seventeen, but her mother remarried. They theorize that June told them her mother was dead because she wanted her to be dead, for not protecting her from her father's abuse or because she was the abuser herself. Stabler thinks they have things backwards. June didn't call her mother over for help dumping the body. Elaine was already there when Marnie came over. Elaine is the killer.
Benson and Stabler interview Elaine at her apartment. It's news to Elaine that June claims she's dead. Elaine describes how June's father spoiled her while she tried to be the disciplinarian. Elaine comments that perfection is not easily attained. Benson asks about Elaine's second husband. He's now deceased, but Elaine describes him as just as weak and useless as her first husband. Elaine says that she was always fair, but firm. Benson suggests that when kids act up, nothing fixes them faster than the handle of a spoon. Benson and Stabler get down to business and ask Elaine about Monday night. They accuse her of abusing Marnie and killing her, then making June clean it up.
Just then, June's younger daughter, Katie, enters the room. Elaine looks to her for an alibi. Katie claims that she dropped her mother off at a bridge tournament in Stamford on Monday night. It's news to Stabler and Benson that Elaine had a daughter by her second husband. Katie immediately starts denying that she did anything. Elaine tells her to shut her mouth. Katie runs off and shuts herself in her bedroom closet. Stabler coaxes her out. That's when Benson and Stabler discover that the bedroom is Katie's - and Elaine's. Stabler and Cap return to talk to June. They tell June that she's going home. They know June didn't kill Marnie. Benson brings Katie in. Katie wants to know why June told them. But June didn't. June apologizes for leaving Katie alone with their mother and not protecting her. Benson and Cap reassure June that none of this is her fault.
Katie makes her confession. She describes how she told June that she was coming over and June told her to use her key because she'd be out, and that she'd canceled her first piano lesson. But then Katie found Marnie on the stoop when she got there. Katie describes how she drugged and molested Marnie and then June came home and saw what she'd done. Benson tells June that she'll have to testify about the abuse Katie and June suffered. Katie won't go to prison, rather, to a psychiatric facility, but she'll never be free again. Benson assures June that Elaine will be going to prison for the ongoing abuse. Katie steps to the mirror, tells June that she loves her. June wonders how she can ever forgive herself after she let her whole family be destroyed. Cap puts an arm around June, tells her that she can start by letting Cap help her try.