Benson and Stabler interview Pamela Burton, whose daughter was kidnapped from inside of her home. Pamela is convinced that one of 10 registered sex offenders in the neighborhood is guilty. The detectives are shocked to hear Mackenzie isn't the only Burton daughter to go missing. Their other daughter, Ella disappeared 10 years earlier.
Surveillance cameras show that 10-year-old MacKenzie left the family apartment building on her own. Benson is shocked by Pamela's overprotection of her daughter. But the one time Pamela didn't monitor her computer time, Mackenzie plotted to run away with a friend named Eddy D in an online chat room. Through the archive chat room, detectives discover Mackenzie was going to meet Eddy at the train station at noon.
After Benson and Stabler find MacKenzie at the train station, they arrest the man she's talking with. Their suspect Eric claims he never had bad intentions, and was trying to convince Mackenzie to go back home to her parents. The detectives don't buy his story. Meanwhile, Mackenzie tells Fin and Munch that Eric is innocent and she left home willingly.
Pamela insists that Benson interview her daughter. Stabler assures Benson he'll work on getting a confession from Eric. Back at the SVU, Mackenzie tells Benson the Burtons adopted her a year ago. She met her online friend Eddy D when she lived at her previous foster home, and they used to wrestle inside his bedroom.
Using Mackenzie's computer, Fin and Munch trace her online buddy's IP address to find a woman named Marie, who denies she's ever seen a guy like Eric before. When the detectives tell her that somebody was using the online name Eddy D on her computer, she accuses her foster son, Wesley. The young boy admits he was chatting with Mackenzie and planning to run away with her, but his foster mother put a stop to their communication, claiming Mackenzie was a bad seed. Meanwhile, Wesley says he misses hanging out with his former foster sister Mackenzie.
Benson discovers that the Burtons really did put a computer chip inside Mackenzie's arm, so if she were to disappear again, police could retrieve all her information. Back at the Burton house, Mackenzie accuses her foster parents of never allowing her any freedom - they only want Ella back. Benson offers to talk to Mackenzie in her room.
Stabler heads to the Burton's vacation cabin to talk to the sheriff who investigated Ella's disappearance, who always suspected Pamela was behind the crime. Back at SVU, Kevin defends his wife - Pamela would never hurt Ella. Kevin breaks down when talking about how happy his family was before Ella went missing.
Using facial recognition, detectives are able to figure out that the redhead's name is Darla, and she was put in the system for being a victim of child pornography. They find Darla working at a seedy massage parlor, and attempt to ask a few questions. Darla refuses to cooperate. Benson and Stabler beg Darla to reveal what happened to Ella that day. Darla breaks down and tells the detectives that her father took Ella, with her help.
Darla tells the detectives that her father wanted to make the 10-year-old Ella his bride, and she had no choice but to help lure the little girl to him. Stabler demands to know where Ella is now. Darla says Ella was caught trying to run away. and her father to beat her to death. That's when Darla ran away and never looked back. Benson and Stabler immediately go to Darla's family farm to search for Ella's body.
At the farm, Benson and Stabler have Darla's father Dale arrested on the spot. He says Darla always made up lies, but the sheriff takes him away. As the detectives look around, they find a young girl cowering behind a tree. Stabler and Benson are shocked to realize that it's Ella. Benson assures the scared girl that she's safe, and promises to take her home. The Burtons begin to cry when Ella walks into their living room and give her a giant hug. Meanwhile, a sad Mackenzie looks on.