Olivia thinks that kissing Peter was only an aftereffects from being in Westfield during last week's reality storm, but now she's migraine-ridden and embarrassed at having kissed Peter. Meanwhile a mental patient named Sean seems to be experiencing a man's home invasion murder remotely and in real time. The case lands in the Fringe team's collective lap, and they interview Sean, who describes his experience of the crime as "hearing voices," like the kind of voice-hearing that landed him in the schizophrenic ward in the first place, only more violent. Walter suspects that since the voices are real, Sean isn't schizophrenic after all, as previously assumed, just telepathically connected to the killers. What a relief, right? Walter decides to test the theory by taking Sean off his meds and seeing what the voices do then.
Olivia's also having some difficulty concentrating on the case, what with having come around to remembering everything about her original timeline. Including, one assumes the Peter and Olivia Sexytimeline. Obviously this is unsettling news to Peter, who's been operating this whole time under the mistaken assumption that he's in the wrong universe with the wrong people. And a session with a suddenly calm Olivia under Walter's magic hair dryer doesn't improve Peter's mood, especially when Walter blames Peter for somehow projecting his memories into Olivia.
Meanwhile, they get a break in the case, suggesting that Sean may be a brother to one or more of the killers -- which is odd, because he was an only child. Except that his mother conceived him with IVF from an anonymous sperm donor, through a clinic that was being looked into by the very man killed early in the episode. Walter forms a theory that Sean and his "voices" are operating as a hive mind, like a colony of bees with a powerful protective instinct, while Peter and Olivia track down the fertility doctor in question at an assisted living facility. That gentleman calmly informs them that he messed with the embryos' DNA (all of which came from his own nasty loins, of course) back in the day, so now his science-demon seed are killing anyone who might make their story public. When Peter and Olivia go to check out a stash of the doc's data, they walk into an ambush, and the doctor himself is killed. Plus, Sean is cut out of the hive mind loop, which he takes pretty hard, even after being comforted by Astrid.
Meanwhile, Walter figures out from a hair sample that Olivia's currently being dosed with cortexiphan -- like, as we speak -- so he and Lincoln go and brace Nina Sharp, all but accusing her of being behind it. And since Nina boasts about being the only one who still has access to the stuff, they soon stop pretending not to be suspicious. After surviving the ambush and closing the case, Olivia and Peter end up kissing for real, even though Peter's understandably gun-shy about repeating the mistake he made with Fauxlivia. And while Walter and Lincoln arrive at Massive Dynamic to find Nina's tightly guarded stash of cortexiphan swapped out for fakes, Olivia disappears from the gas station where she and Peter stopped. She wakes up, beaten and bound to a chair in a dank basement, facing an equally battered… Nina Sharp. The real one, I assume, and not the presumably fake Nina currently enduring the accusatory stares of Walter and Lincoln. On the bright side, at least now we know the real Nina isn't evil. Unless of course she beat up a Mark Two shapeshifter that looks like herself and stuffed her in a basement with Olivia. Probably shouldn't rule anything out.
We pick up from where we left off last week, with Olivia kissing a very surprised Peter, who inexplicably didn't just go with it. Instead they sit down and Peter wants to know if Olivia's OK, and she says she is. "Then why did you kiss me?" asks Peter, because clearly it's a sign that something is very amiss if someone wants to kiss him. Olivia says it just felt normal, like it's what they would do.
She's perfectly aware of who she is and who Peter is, she says, and she thinks this is just residual effects from being welcomed to Westfield, and she deflects Peter's suggestion that she should let Walter have a look at her. "I think what I need is just some rest. I'm sorry that I kissed you. To be honest, I'm a little bit embarrassed about it." He offers to stay, just to make sure she's OK (with sexy results, I'm sure), but she says she wants time alone and she thinks she's got another migraine coming on, and he leaves, but first wrangles a promise from her that she'll see Walter in the morning if she's still feeling wonky. She closes the door on him, and then flashes back to that time the other Olivia came over for her date with Peter and he was all glimmery, which was when we all knew that Peter was from the other universe.
Welcome to Deerfield (Mental Hospital), where a young man is shuffling around in the dead of night in his pajamas and bathrobe, shushing someone, although he's the only one around. He goes to the window of what appears to be the cafeteria. "It's time," he says.
And we immediately jump to Douglaston, New York, where a trio of ne'er-do-wells are entering a home that is not their own. Back at Deerfield, the young guy whispers, "He's in the kitchen." In Douglaston, there is indeed a middle-aged man in the kitchen, burning himself on some popcorn that he's taking out of the microwave.
The Deerfield kid whispers for the three guys in Douglaston to fan out, which they do, while the man in the kitchen empties the bag of popcorn into a bowl, and somehow manages not to have either tons of kernels left over or that clump of browned and burnt popcorn. But the Deerfield mastermind is interrupted by a woman named Bernadette, who comes into the kitchen and calls him "Sean" and says he should be in bed. He resists somewhat, but then acquiesces as Bernadette leads him down the hall, telling him that the voices he's hearing in his head aren't real. Then he stops when the popcorn man leaves the kitchen. "He's coming your way. He's coming your way," Sean says, as though the three young lads are in some sort of danger from the middle-aged man with the bowl of popcorn who doesn't even know they're there. He's startled and drops his popcorn when he spots one (who has a knife) and then another, and then he backs his way up the stairs, frantically telling them they can take whatever they want, only to be jumped from behind by the third thug, who wraps a plastic bag around the man's head and then all three of them start attacking the guy, breaking a glass door in the process. Plus the whole place now stinks like that nasty fake butter they put on microwave popcorn, so this is a tragedy in so many ways.