Braydon and Josie Leddy, a young New York couple, are at the park with their one-year-old daughter, Tessa. Their daughter is abducted while the couple is tending to business phone calls, and the SVU unit is quickly called in to investigate. Luckily, Braydon films his daughter's every move with his cell phone camera, and the detectives are able to identify a suspicious character in the background of Braydon's video. Fin and Rollins head to the suspect's home to investigate.
Fin and Rollins arrive at the apartment of Allen Clyde, a convicted sex offender, but there's no sign of the Leddy's missing daughter. Clyde tells the detectives that he saw Tessa leaving with her mother, a blonde woman in a floral print dress. Another analysis of Braydon's videos leads them to the woman Clyde singled out. They head to Tessa's nanny's home to question her about the mysterious woman.
Tessa's nanny gives the detectives a photo that she received from the mysterious woman, which features a website URL for the suspect's photography business, lifemomentsbydia.com. The detectives are able to find the woman's name and they head to Dia's apartment in search of Tessa. They arrive to find Dia caring for Tessa in a replica of Tessa's bedroom. Dia claims that she's Tessa's birth mother and that she has the documents to prove it. They've found the missing child, along with a load of unanswered questions.
After some DNA tests and document analysis, the detectives discover that Dia's paperwork checks out, and unbeknownst to them, Braydon and Josie's paperwork proves fraudulent. DNA tests confirm that Braydon is not Tessa's father, which means the Leddys were bamboozled by their surrogate lawyer. Dia points the detectives to Tessa's real father, a high-profile lawyer named Kent Webster.
Benson and Rollins locate Kent Webster, who claims that he met Dia once at a photo shoot and that she began stalking him shortly thereafter. The detectives are suspicious because Dia knows personal information about Walker. The conversation is interrupted when Webster receives a phone call from his daughter, who tells him that Dia showed up at Webster's home.
Rollins, Benson and Webster arrive at Webster's home to find Dia involved in a confrontation with Webster's sick wife, Gillian. After the altercation is broken up, Dia tells Rollins that she's been involved in an affair with Webster for the past year and that she has phone calls, text messages and lewd photos to prove it. This case just keeps getting better.
Fin learns from Webster that he and Dia were briefly involved after the photo shoot a year ago, but that they did not have sexual intercourse. However, Fin believes that Dia could have gotten Webster's semen and impregnated herself in some other way with Webster's child. Benson and Amaro talk with Webster's sick wife, Gillian, who has been weakened by a traumatic brain tumor and can't even lift a water pitcher.
Later, Rollins and Benson meet with M.E. Warner, who informs them that DNA tests indicate that Webster and Dia are Tessa's biological parents. In court, a judge releases Tessa to the custody of the state until the detectives have time to sort out the parental dispute. Meanwhile, they also learn that the Leddy's crooked surrogate lawyer was hired by Webster's father, apparently to clean up his son's mess.
While speaking with Webster again at a restaurant, Webster's daughter Hannah brings a shocking revelation to light: Dia has posted photos of she and Webster canoodling and holding hands, and the photos were taken that same day. Webster's wife and daughter can't dispute the photo evidence, and Webster has some serious explaining to do.
The detectives are sorting out the details in the bullpen when they receive a distress call from Dia's apartment. When they arrive on the scene, they find Dia dead on the floor and Webster sifting through her personal belongings. Webster claims that he found Dia dead, but the detectives bring him in for further questioning.
In the interrogation room, Webster stands by his claim that he didn't murder Dia, but that he was at Dia's apartment to retrieve some sex tapes that she threatened to release to Webster's family. Warner confirms Webster's claim: Dia was bludgeoned over the head with a heavy object while Webster was still at his office, which means that someone else had it out for Dia. Despite her illness, Webster's wife is the most likely suspect.
Amaro finds a 911 call that came in while Webster was in Dia's apartment. The voice on the 911 recording is clearly that of Gillian Webster, who framed her husband. The detectives head over to question Gillian. During the stressful interrogation, Gillian passes out and is rushed to the hospital with her daughter, Hannah, by her side. Amaro and Benson join them in the hospital room.
Benson is having trouble figuring out how Gillian managed to bash Dia over the head with a heavy object, considering that she couldn't even lift a water pitcher earlier. Suddenly, the truth begins to reveal itself, and Benson suspects that Webster's 15-year-old daughter, Hannah, is the actual murderer. Nonetheless, Gillian admits to the crime, implying that taking the fall for this crime is the last thing she'll be able to do for her daughter. Benson has a decision to make.
Back at the station, Benson and Amaro prepare to brief Cragen. Before Cragen arrives, Benson gives Amaro an out, saying that he doesn't have to be involved in this if he's uncomfortable with it. Nevertheless, Amaro sticks by his partner. Benson lies to Cragen and puts the blame for Dia's murder on Gillian, who is later found guilty of manslaughter in court while her daughter is able to go free. Benson is still not sure if she did the right thing.