Oh, and Walter's got a theory as to how the larvae can be tricked into self-destructing, says Peter, who says they need to mix some of the creature's blood in with Charlie's own: "That way, maybe the larvae will think he's one of their own and stop feeding and die of starvation." That's so crazy it just might work! Why don't people say that anymore?
Anyway, Olivia's on board with the plan, and Broyles asks her what's up. "We need to find the creature," says Olivia. Well, easy enough, right?
Back at the playground, the woman's still on her cell phone with her friend talking about some house, and her son, Tuck, is running around all over the place, and goes into one of the pipes connected to the one the monster's hiding in. Finally, Mommy sees something through one of the vent holes in the side of the pipe, hangs up and goes after her son before he becomes Tuck, Decidedly Non-Everlasting, and we hear some movement and snarls, and background screams, as the beast decides to go for a little walk, apparently.
Back at the lab, Olivia's looking at a map, at the different places where there've been sightings, and she can't figure out why there haven't been more reports. Meanwhile, Walter's giving Charlie a sedative to relax him. "I'm sorry this has happened to you," says Walter, and Charlie's all, "It's not your fault," and Walter's all, "Yeah, the funny thing about that is..." but he doesn't get a chance to tell Charlie where the creature came from before Olivia excitedly asks Astrid for a schematic of the sewers, because she thinks the creature's traveling underground.
Fortunately, Astrid gets the translucent schematic so its easy to overlay onto the map (fortunately in the exact same scale) and they can see that the sightings are all near major storm drains. Walter says it makes sense: "If it's part tiger, then it would prefer dark. And a python would seek out water." Peter guesses it's only surfacing to eat or... to mate, and then he's suddenly quiet, and his dad is all bummed out again, because if the creature is traveling in the sewer, then it could be anywhere. Well, wouldn't that be even more true if the creature were traveling above ground? Olivia tells him it's OK, that they're making progress. "No, it's not OK! You tell Agent Francis it's OK!" he snaps, and Peter says he'll go talk to him.
Before he gets the chance, though, Charlie starts groaning loudly, and the Fringe team (minus Walter) rushes to his bedside, holds him down and lifts his shirt. We can see the larvae writhing around through the skin on his abdomen. "They're getting bigger," says Peter.