Speaking of work, Olivia's at home looking up "monarch" in her FBI Google, or whatever that is, before she decides to get some rest. She crawls into bed -- and her computer reboots. Puzzled, she goes back to it to find an e-mail from John Scott. She stares at the message for a good long while. But she's going in. Of course she is. It's one of this show's trademark "underground abandoned steam shovels" sets. She comes into a room with blue bins stacked all over the place. Olivia finds a bare light bulb and turns it on. Opening up one of the bins, she finds a bunch of frogs, croaking and trying to get out. Startled, she closes the bin and steps back.
The next day at Boston Federal Building, Charlie's all, "Uh, do you know anything about a bunch of frogs?" He just got a PO request from Astrid for a terrarium and ten pounds of live insect larvae. "Is there something you want to talk to me about?" Olivia's cagey about the details (he asks if the frogs had something to do with Mark jumping out the window) because she's got something else on her mind, and she pulls Charlie aside so she can talk about how she's losing her shit: "I feel like I'm going clinically insane, literally. I told you I saw him standing right in front of me." Charlie asks if it's happened again, and Olivia says he's called her, sent her e-mail, sent her a friend request on Facebook -- he won't leave her alone! He suggests talking to Dr. Katz, but she doesn't want a psych eval on her record. She just wants to take some personal leave. Charlie asks if that'll help, and Olivia says she doesn't know. Her phone rings. It's Astrid, saying Walter needs her back at the lab, because he thinks she's cracked the case: "You are not going to believe this, but, um, the guy who jumped out the window? Dr. Bishop thinks it's because of the frogs."
Where's Peter, anyway? He's in some diner, hugging a woman who says she wasn't sure he'd be there. "That makes two of us," he says. They sit down at a table. He tells this "Tess" that she looks good, and she tells him he looks older. When he tells her his father said he thought Peter would be fatter, she's surprised to learn that he sees his father now. Peter calls it a "long story." But let's get down to it: Tess says if she can find him, then they can find him. Peter says he knows. "They'll hurt you," says Tess, which seems to me to be something that he would likewise already know. He ignores this and asks if he can get her a cup of coffee or something to eat. So she starts crabbing about how nothing ever changes with him, and he plays it "fast and loose until it's too late," like HOW NICE TO SEE YOU AGAIN, TESS. She says, "I mean, it was easy enough for you to leave the first time. Why should it be any different now, right?" Peter says she has to trust him that it was harder than she thinks. She's all, "Trust you? I'm not sure I ever even knew you" and Peter says she did, better than anyone, and he takes her hand, looking all tender, and at this point I'm mainlining caffeine just to keep my eyes open, and she tells him he needs to leave Boston and never come back, ever. "Is that what you want me to do?" asks Peter. She starts to pull back, and he holds her wrist. She winces, and he looks at her wrist, which is badly bruised with what's clearly finger marks. "Michael?" says Peter. "Things have changed," she says, and Peter says, "Yeah, apparently." "It'll be worse for you if you stay," she says, and she gets up and stomps out of the diner. Peter stays there. I came all the way downtown for this?
Back at the lab, Walter's set up an old film projector because they're going to be watching movies instead of doing any work! This movie stars Walter himself examining some guy, as Walter at Harvard drones on about "psycho-physiologic effect, otherwise known as psychosomatic," which is the ability of the mind to cause actual physical changes in the body. And since Peter's not there, I guess Astrid is the Deputy Agent in Charge of Explaining Walter's Explanations in Layman's Terms, and she calls it "mind over matter," like when you get scared and get goosebumps, and Walter says "precisely!" and Peter better watch himself, because without his explaining duties, all he really brings to the team is three day's growth of beard.
Walter explains that the test subject in the film ("the archive footage," Walter helpfully explains, just in case Olivia and Astrid were wondering if he shot this this morning) is in a highly suggestible state, and we watch him do exactly what Walter indicates. Real-life Walter chuckles and then says he convinced the guy that he was in a meat locker. "And what is more impressive, I told him that this ice cube was a burning coal." We see Film Walter take an ice cube and run it along the guy's right arm. The guy screams in agony -- standard stuff for a hypnosis performance, but this guy's skin actually reddens and blisters. "Oh my god!" says Astrid. Keep it together, agent. Olivia asks what this has to do with frogs. "Toads, actually," says Walter, who explains that they're a species that secretes a psychoactive compound. There was a substance in Young's blood that he couldn't identify, and it turns out it's a concentration of the venom produced in the skin of the frog. "Properly altered, it's an hallucinogen, a very powerful one. Quite unlike anything I have taken," says Walter, practically smiling, thinking about dropping acid, I suppose. He continues: "It directly affects the amygdala, which is the fear centre of the brain.
Olivia's already piecing it together: "You're saying that Mark Young hallucinated being cut on his body, and then his mind made it actually happen." Walter calls it a clever means of murder and Olivia's all who in the what now? And Walter gets a little testy, saying, "Oh come on, we discussed this," and if anyone ought not to get upset with people not remembering things, it's Walter, and Astrid calms him down by reminding him that he discussed it with her before Olivia got there. Walter explains that the potency of the drug in Young's blood was at least thirty times the amount that any sane person would ingest: "Which suggests that someone else gave him the drugs," he says. I guess? So Walter's never heard of drug overdoses then. "So whoever those frogs belong to may be the killer," says Olivia, starting to look a little antsy. Astrid tells her she ran a property search on the basement where Olivia found the toads, but nothing came up. "How'd you even find it in the first place?" "It's a long story," says Olivia, an explanation that appears to be good enough for Astrid.
With Walter a moment later, she's a little more forthcoming. She tells him that John Scott led her to the shed where she found the frogs. "You've been seeing him again. Because his memories are still in your head," he tells her, explaining that they're trapped like fragments. Snapshots in her mind. "Your work on this case must be a trigger to some knowledge he had," he says. Olivia asks how long this is going to keep happening. "Could last for many years," says Walter. Olivia says she can't keep having John's life flash in front of her eyes every few days and says there must be something Walter can do. "Perhaps. Using a form of repressed memory therapy, we may be able to bring the memories to the surface, and purge them from your unconscious. But..." he trails off, shaking his head, starting to walk away. She figures it out: "You'd have to put me back in the tank." Yeah, that's right, and Walter advises against it, saying th