Back in the sewers, the gang sits around waiting for the monster, and Walter says in a frightening situation like this, he's reminded of a couple of things: "The first is a song I used to sing to Rufus," which was the Bishops' dog, because the dog used to have night terrors, and he starts singing this old song about a guy named Van Amburgh who sticks his head in a lion's cage, or some damn thing, at least until Peter says, "Think we can wait down here to be mauled in silence?" Like, is that what you'd like your potentially last words to your father to be? Walter, chastened, quiets down, except Olivia reminds him that he said he was reminded of two things. "Oh, the second thing. I need to tinkle," he says, and asks if either of them can direct him to "the facilities" -- like, first of all, it's not like Peter or Olivia have ever been there before, and second of all, as Peter points out, "You're in the sewer, Walter. You're knee-deep in the facilities."
So Walter steps away, surreptitiously putting his gun in his pocket, and Peter says to Olivia, "Don't say that I never take you anywhere," like how nice to start hitting on her now. And their flirtation is interrupted when Walter clangs shut a metal screen door and uses a crowbar or metal rod or something to bar it shut as Olivia and Walter rush up to it. Peter orders Walter to open it. "I'm afraid I can't do that, Peter. No one else is going to get hurt. This thing is a mistake, and I'm going to correct it, alone." Peter yells again for Walter to open the door, and Walter says it's like Peter pointed out: "I live in a society. And I need to clean up after myself." You happy now, Peter? This is all because your dad didn't want you to eat his ear omelette!
Peter points out that this creature wasn't the result of Walter's work, and Walter says it could have been, because he was pursuing the same science.
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.