Back at Fringe HQ, nobody is working since Olivia's not around to make frowny faces at them, so they're eating Chinese food and watching Spongebob Squarepants. Walter loves it. Peter answers the phone with "Nuthouse," and it's Olivia telling him she needs him and his father when they go after Steig so Walter can question Steig and make a vaccine. Peter says they'll meet her outside, and manages not to call her sweetheart.
So Olivia sets up with the rest of the FBI assault team outside Steig's apartment, because you know how she loves her first-hand knowledge and everything. The team goes in. There's no one in the place, but there's a rug with a corner sticking up at an odd angle, so Olivia lifts it up and finds a trap-door underneath, and underneath that, a little laboratory with computers and caged animals. It looks exactly like the setup in the storage locker. Perhaps he just sometimes felt like driving for hours?
Meanwhile, in the car, Peter is looking over the FBI file on Steig -- nice of Olivia to just leave it lying around like that -- while Walter frets about his son showing signs of hypertension.
"When this is over, please don't send me back," says Walter. "This experience -- you woke me up; you can't just put me back to sleep." Peter says none of this was his idea. Walter says that whatever punishment Peter thinks he deserves, he swears he's already endured it. Peter doesn't respond. But it's a good thing he's out in the car, because even with all the dozens of agents in this assault team, nobody is stationed by the BACK DOOR, and here comes Steig out the door and down the alley. Peter starts yelling, and chases after him, across streets, dodging traffic, and down steps. Olivia follows. Steig runs into an apartment building, and through units, and then up onto the rooftop, and leaping over onto the next fire escape -- it's all very Bourne Ultimatum. Olivia hurtles from the rooftop onto the fire escape, and then down onto a Dumpster. She's doing all right for someone who was recently drugged and given a skull implant and mind-melded with her comatose brother. Hey, where's Peter? Oh, there he is -- pulling the ol' "I'm behind you and then somehow I just appear in front of you" routine, knocking Steig down and then pounding the ever-lovin' shit out of him. Olivia finally shows up -- good thing, since the rest of the FBI is nowhere in sight -- and you think she's going to pull Peter off Steig before Peter beats him to death. Instead she just sticks a gun in Steig's face and snarls, "We've got some questions." Question one: which Steven Seagal scriptwriter is handling this dialogue?