Peter's got to try to convince the Fringe team that he really is who he says he is, which is difficult since no one has any memories of him, which they'd probably be pretty excited about if they knew what was going on. Plus they're trying to track down another shapeshifter, which has killed another couple of people in an attempt to track down a former Massive Dynamic scientist. She/he/it or whatever needs the scientist, Truss, to stabilize her fluctuating skin, which he agrees to do under the misconception that this person is actually a cancer patient who was treated with cell replication therapy based on old work he did for Massive Dynamic. Peter helps them by hacking the shapeshifter 2.0 device they have (after earning a shot based on his knowledge of the old shapeshifters), and they track down the shapeshifter and save the scientist. The shapeshifter gets away, though. I mean, not at first. At first the Fringe team forgets that the last person to see the shapeshifter ALWAYS turns out to have actually been the shapeshifter, even if there really wasn't enough time for her to change bodies and dispose of the other body.
Anyway, after looking into Peter's eyes, Walter knows that Peter is his son -- or at least an iteration of his son from yet another universe -- but the guilt he's carried since both young Peters died (along with the anger at acting Massive Dynamic CEO and Olivia's adopted mommy Nina Sharp, who he blames for the second Peter's death) means that he doesn't believe he deserves a second chance (or, really, a third chance) with Peter and so ditches his son. Maybe he can try again with Olivia, who's confused by Lincoln Lee rejecting her advances -- and also unable to explain why, if Peter's a stranger, he's been popping up in her dreams. You know, apart from being a fox, amirite?
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Elsewhere, Olivia shows up in the lab but there's no sign of Walter or Astrid. There is, however, a beeping sound that gets faster after a moment, as she heads to the back of the lab, where she finds Walter sitting in a chair, hooked up to some sort of intravenous apparatus that, as she approaches, injects a light blue liquid. Olivia urgently calls Walter's name, and after a moment he snaps awake, a little disconcerted to awaken to Olivia yelling at him.
She's relieved, at least, that Walter's awake, but a little concerned with Walter explaining that one syringe has sodium thiopental to help him sleep and the other one has adrenalin to wake him up. Like, did you ever hear of an alarm clock, Walter? Olivia wants to know, "Who sleeps like this?!" Just hipsters, now. Later, everyone.
Walter starts whining about a bunch of first-world problems, like this guy from his hallucinations who has shown up and is real, but no one will let Walter examine or even see him. Anyway, this is why he can't sleep.
Walter asks Olivia if the guy is speaking, and Olivia explains that he was, but has stopped cooperating so Broyles had him moved to a holding facility in the Federal Building and says Walter's the only person he'll speak to, which surprises Walter. "He's saying that his name is Peter Bishop. He says he's your son," says Olivia. Little more adrenalin for you there, Walter? Kinda looks like you could use it.
In Hillsdale, New York, a truck pulls up at a residence and a literally blue-collar guy walks into the house, where a woman is ransacking the drawers. "Hello," he says, and she stops what she's doing, and says hi. He stares at her for a moment and then finally says, "I thought you said you hated that sweater," and she, sounding like she's lying, says she thought she'd give it a second chance.