When a 15-year-old girl named Lily goes missing, SVU seeks to return her to her parents. Sgt. Mike Dodds (Andy Karl) assumes it's a cut-and-dry teenage runaway case, but while tracking Lily's debit card, the team finds her body, and a murder investigation begins.
DNA on Lily shows a partial genetic match, meaning the killer was likely a relative. SVU interviews Brendan, a relative whose DNA is in the system, and asks for a list of his male family members. However, Brendan turns out to be adopted, and his birth father, Ray Marino, died 5 years ago. Det. Sonny Carisi (Peter Scanavino) and Dodds interrogate Ray's two sons from a second mother, but the DNA doesn't match either brother, though the killer is still related to them. Stumped, they have Ray's body exhumed and his DNA tested and learn he had at least one more son, with a third mother. After another exhaustive search through Ray's family tree, SVU finds a DNA match in Gary, a delivery driver.
Dealing with his first special victim, Dodds feels partly responsible for the tragedy because he jumped to the wrong conclusion when Lily went missing. He interrogates Gary with the hope of determining that there was really nothing he could've done. Indeed, Gary admits he was flirting with Lily, and when she accepted a ride, he tried to kiss her. Lily denied the advance and the situation quickly escalated. Gary forced her into the back of the van where he shook her, hitting her head on the floor of the van, where she died from blunt force trauma. Despite solving the murder, Dodds still feels hung up on the case. Lt. Olivia Benson (Mariska Hargitay) gives him some advice for letting go of work when the day's done.