Olivia asks who was overseeing the project. Turns out it was Lane Pryce. I mean, David Robert Jones.
Over at the Harvard lab, Lincoln is plowing through the sandwiches Walter made. Well, he's actually just picking off the bacon and eating that. Maybe one of the characteristics of the engineered mutation is that people with the virus eat their feelings! Lincoln wants more bacon. MORE BACON. Walter calls for "Aphid" to provide some, and then something dawns on him: He asks Lincoln what else he's hungry for -- pickled herrings, spinach? Lee says he doesn't know, but some onion rings would be nice, maybe some cheesecake. Sounds like the Betty Draper off-season diet! Lincoln trails off, staring at Walter's midsection. Walter grabs his own love handle, and then tells Lincoln to call Peter and Olivia, and tell them he understands.
I guess it's Aphid who wound up calling, since Peter and Olivia rush in having been told by her that he made a breakthrough. "Agent Lee is infected. We know for sure now," says Walter, and Peter's a little confused by Walter's giddiness. "He says I'm gonna be fine, by the way," chimes in Lincoln, much calmer than he had been.
See, Walter's figured out what the creatures needs to fuel its metamorphosis: Lipids! Walter brandishes a bag of human fat, which was what was in the medical waste bags, most likely vacuumed during liposuction. "Fat stores concentrated energy, and energy is necessary for transformation," he says. He knows what they're thinking: Wouldn't it just be easier to eat people? Actually I was thinking that I can probably make it to the toilet before I vomit if I move really quickly. Anyway, the answer is no -- not with 300,000 pounds of fat being disposed of by plastic-surgery clinics every three months.
Olivia says they need to make a list of all the cosmetic-surgery clinics and see if any of them have had any medical waste stolen. Astrid says she's on it, but notes that they might not be inclined to admit. So play good Fringe agent, bad Fringe agent with them! You'll break them down.
Peter's got another more prosaic question: How are these creatures able to get around without being seen? Walter's at a loss, but we're going to see the answer. We head over to where Porcupine Man is on a roof with his... well, girlfriend, I suppose. They're standing on the ledge, and she climbs into his arms, and he spreads bat-like wings and they fly off into the night. Body of a porcupine, wings of a bat -- you can really see what she's hot for this guy.