Peter yells at his dad for almost killing a guy because he injected stuff into his brain twenty years ago. I had this exact same conversation with my dad not two days ago! Walter protests that he didn't put nearly enough in to cause that kind of reaction; it must have multiplied in his system over time. "Environment, diet," he says. Yeah. Roy's had a couple extra Big Macs too many. That's how all the metal in his blood got there. Peter asks (well, yells, really) if his dad ever explained to Roy what he was doing, and Walter points out, not completely unreasonably, that it wouldn't have been much of a secret experiment if he had.
Olivia comes in and asks what's going on, and how Roy is. Peter says Roy's fine, "no thanks to my father's attempts to turn him into a human walkie-talkie!" Hey, that's it! The compound in the blood has turned him into a receiver of transmissions. "Someone else, it seems, and I'm jealous of this, has perfected our ghost network, and is using it to communicate. Our dear Roy is merely overhearing what they say." But ... the visions?
Well, fortunately, Walter's got some confusing things to say about that, with a handy-dandy slide show that depicts some familiar optical illusions, and says Roy's brain is attempting to interpret the sensory input he's getting through the ghost network. Well, since his depictions are so bang-on, it appears his brain is doing a fantastic job interpreting, doesn't it?
So what do they do, work on their own receiver? No, don't be foolish; that'd take too long! Walter wants to do some minor brain surgery on Roy to send the confusing visuals to his auditory cortex instead, and I don't have to be a scientist to know that this all sounds ridiculous. Not to mention FATAL. But no, this is a great idea. Walter just needs some piece of equipment that he has hidden in a wall in his old house in Cambridge, a "magnetic neuro-stimulator."
This means an errand out to the house for Peter and Olivia for some sort of equipment that'll help Walter do brain surgery. No one appears to be at home, so Olivia tries to get in touch with the owners for consent, which you'd think she'd have done LONG ago, but Peter just goes ahead and breaks in. He calls it "barely a crime" since he used to live there.