Olivia tries reasoning with him, saying he's not prepared for this: "That thing could tear you apart," she says, and Walter's all, "Yeah, that reminds me!" And he pulls out the bottle of trichlorimide, and chugs it. Peter freaks out, and Walter says, "Should the creature consume me, it will only be poisoning itself. Afterwards, you remove its blood and save Agent Francis." Yeah, but... wouldn't the trichlorimide then be in the monster's blood? Walter ignores Peter's pleas not to do this, and says, "Should I live, there's an antidote in the lab, which I should ingest within the hour. So time is of the essence," and strolls away, Peter screaming and banging on the door after him.
After the commercial break, Walter walks through the sewers, singing his Van Amburgh song quietly, and we can hear the sound of something snarling in the distance. Somewhere behind him, Peter and Olivia frantically work to pry the door open, with Peter promising, "If he lives through this, I am gonna kill him myself."
Walter keeps singing the song, carefully making his way around the corner, seeming somewhat relieved when his face isn't eaten. Only then he seems to have come to a dead end (or just a way up to another manhole). He turns around, and hears something faint, and sees something dripping in a puddle near his feet. He looks up, and we see just the claws first as something climbs down upside-down onto the ceiling. A lizardy thing, huge teeth, snarling and menacing, tail uncoiling and rattling behind it. "Oh, dear God," says Walter. This is just when Peter and Olivia come running up, and Peter yells for his dad. The creature swivels to look at them, snarls and drops to the ground, knocking Walter over before lunging at Peter and Olivia. We hear gunshots, and suddenly the thing is on the ground. That's it? All it took was a couple of bullets? Shit, I could have taken a couple of bullets and still finished my lunging. Walter's holding the smoking gun, his hands shaking. Peter asks if he's OK. "Yes. Although when I mentioned that the poison would kill me within the hour, did either of you happen to notice the time?" Probably not a good idea to mention that you'd think a genius would have remembered to bring the antidote along too, just in case.
Back at the lab, we get the Montage of Science-Type Things Happening, with beakers of fluids and syringes and that spinny thing the you use to mix solutions, and then Walter injects something into Charlie and hooks him up to an IV bag, Charlie says, "That's it, then?" Yeah, that's pretty much it. Walter tells Astrid to prepare Charlie for the ultrasound. Which gives Charlie enough time to weakly tell Olivia that he and Sonia have been talking a lot lately about having a baby, and Astrid interrupts so she can gel him up.