She calls Olivia's comms device and asks to speak to Walter -- whose archival search has come up empty for any trace of a visit here -- to tell him about the mine that he's supposed to find. Not sure why she couldn't have explained that to Olivia, but maybe it was so that we could waste some time on Walter thinking Astrid said "mime" and be confused about what Marcel Marceau has to do with any of this. Walter asks Edwin if there's a mine in the area. There is; a gold mine.
Over in Manhattan (the one in New York, if you're wondering), Windmark is glowering out the window at the city below him when another Observer comes in with a couple of loyalists, saying these men have something to report. They show him a holographic recording of the Fringe crew changing a tire on the van. Windmark sits watching it impassively, before finally asking, simply, "Where?" Rural Pennsylvania is the answer.
The Fringers stroll into the mine, treated to Walter's recitation of the details of a mine collapse in Peru in 1923 in which the trapped survivors were forced to eat the dead. Peter says it won't be easy to find gold in an abandoned gold mine, and Walter points out that they don't know what they're looking for is gold.
They come to a mine shaft with a rope dangling over the side and into the darkness. Peter offers to climb down, but Etta tries pulling on the rope first. It's too heavy for her to pull up on her own, so Peter gives her a hand while grousing about how he doubts whatever they're supposed to be looking for is just going to be waiting for them after two decades, like FEEL FREE TO SUPPLY ANY BETTER IDEAS, PETER.
Whatever's on the other end gets snagged on something, so it requires a good yank -- and flying up comes a disgusting, blackened corpse, covered with the same bark as the people in the camp, only much, much worse, like a marshmallow that caught fire and burned.
Walter, snapping off a finger to examine it (and maybe also because hey, free fingers, right?) says he'd assumed the growth was some sort of fungus, but he was wrong, because this person's tissues show some sort of calcification. "Perhaps whatever was causing the condition of the people in the camp is emanating from this mine. And the closer one gets to the source, the more intense the reaction is," he says. With death-by-spelunking a very real possibility, he orders everyone out of the mine until he can conduct an analysis.