Peter and Olivia stroll across the Harvard campus, with Peter shaking his head at how crazy the whole deal is, and how none of the people here have any idea. "If we do our job, they'll never have to," says Olivia, like that's supposed to make Peter feel any better. Charlie calls on Olivia's cell to tell them that the brain-snot thing has happened again, to a day trader outside Chicago. "When are you going to start calling them murders?" Olivia asks Charlie for some reason, and Charlie says, "When you find us a murderer." Olivia asks him to send her everything he's got on the victim.
They're about to head up the steps into the building when they notice an older woman staring at them. Peter says he'll meet Olivia inside, and walks over to talk to her, while Olivia slowly goes up, watching Peter.
"Are you Jessica Warren?" he asks the woman, who says she is. "I'm Peter Bishop," he says, and she says she knows. He tells her that he read her letter, and he understands why she wants to see his father. "But it's not the right time," he says, because his dad just got out of the institution. "After seventeen years--" he begins, and she interrupts him to snap, "And three months. I know how long it's been." "I'm sure you do," says Peter, not unkindly. He says he's very sorry, but nothing will bring her daughter back, not even talking to Walter. To be fair, if you were looking for someone to raise the dead, Walter's probably your guy. Jessica says she needs to talk to him. "To do what, to blame him for the accident?" says Peter. Jessica says it's between her and Walter, WHICH IT IS, PETER, but he says "It's not going to happen" and walks away.
Inside the lab, Astrid greets Olivia by saying that she's glad Ella's OK. The closed-captioning tells me that a toilet is flushing, which I can barely hear, but it does help explain why Walter comes out of a little room playing with his crotch. He excitedly tells Olivia that he's figured out what's going on. Something to do with a complex combination of "visual and subsonic aural stimuli" that amplify the electrical impulses of the brain, trapping it an endless loop. Olivia interrupts him because she doesn't understand, and Peter isn't there so Astrid pinch-hits and says it's like a computer virus that infects people.
Olivia's in her office shuffling some TPS reports when Peter comes in to ask a couple of rudimentary questions about the latest victim, but mainly so Olivia can tell him she knows who the woman was outside. Peter asks her what she thinks she knows. "That she's the mother of the lab assistant that was killed in a fire here almost twenty years ago." Yeah, that's pretty much it! Speaking of which, there isn't any fire damage in the lab. So I guess that means this fire did enough damage that it killed a woman, and Walter got sent to a mental hospital, and Harvard? I guess? Repaired the damage, replaced any destroyed equipment, returned the lab to the way Walter had it, and then shuttered it for the past seventeen years to wait for his return?