Olivia tells Cragen the rape kit was negative; Cooper must have worn a condom. Also, they didn't find any of Cooper's prints at the warehouse. Chester's got some news: Cooper's real name is Gregory Searle, who did time 25 years ago for kidnapped 15-year-old Lauren Molby. There's a picture of her too; it's the girl from the picture in Cooper's apartment. "Cooper decided to relive the glory of his old crime in virtual reality," says Chester.
So Cooper snatched Lauren out of her bedroom; she was never found, and the D.A. was convinced he killed her. Well, maybe the detectives can ask him about that; he's been found at a bus station, heading for Montreal.
Chester's the one who confronts Cooper before he gets on the bus. Fin snarls that "Canada's closed" and they haul him off to the hospital so Rachel can ID his voice. They're too late, though; Olivia makes her way over from consoling a grieving father and sister to tell them Rachel didn't make it.
A fruitless interrogation follows, with Cooper maintaining his innocence and pinning everything on Nestor (the warehouse belongs to the store and Nestor has a key, that kind of thing). Since they don't actually have anything on Cooper, they need a confession or he walks. Huang advises a frustrated Elliot and Olivia to try to get him talking about Lauren, which may lead him into talking about Rachel.
Cooper considers himself a hero because he rescued Lauren from an abusive dad and a drunk mom. "We loved each other. You don't forget the best year of your life!" he says, saying they had a place (but he won't say where it was). He also says the day before he was caught, he told Lauren she could go, but she said no, "out of love." Elliot segues into Rachel, who wouldn't stay with him unless he drugged her. But Cooper's figured out that he's been for hours and hasn't been charged yet, because they've nothing, and he gets up to leave.
Casey suggests finding Lauren's body, charging him with murder and then using that crime to establish precedent. "Hey, maybe it's in the game!" suggests Olivia, since Cooper's always talking about a cabin in the woods. "Maybe he built a digital dream house that can lead us to Lauren's body," she says. Casey figures it'll work, so Olivia heads over to talk to Wynton while Elliot tails Cooper to keep an eye on him.
Sure enough, Cooper's used the game software to build a cabin and a lake. Inside we find an avatar Cooper created: a girl sleeping on a bed with "Lauren" written on it. "I bet you this is a virtual replica of the (cabin) he used to stash Lauren," says Olivia. Fortunately, Wynton's got some preposterous software that'll instantly compare the Another Youniverse lake to a database of actual New York bodies of water, and Fin and Chester head upstate to be there whenever the lake is identified. Wynton gets it on the third try, and Fin and Chester are on their way to Twin Island Lakes. Elliot urges them to hurry, since it now appears Cooper's on his way to La Guardia. And hey, could we get a little more preposterous for the last few minutes of the episode?