And then Fauxlivia comes in, and because she now knows she needs to be super concerned about how Walter's doing, she's brought him some malassadas, which I don't think I've ever even heard of but Walter goes nuts for them. She asks if there's anything new in the book, and Astrid says, "I'm sure the numbers hold the answers. But beyond that, nothing tangible."

And then Peter finds something: the transistor that we saw Feller solder, and Peter can tell it's Polish, and military grade, and there are only a couple of places that are licensed to sell things like this, and you have to have a verified address to buy one. Fauxlivia takes in all this information impassively, and when Walter borrows the First People book to take with him to the crapper, grossing out Astrid in particular, Fauxlivia excuses herself to update Broyles. She looks pissed.

And then she actually leaves rubber driving out of there. I guess part of her cover story is that none of the phones at Harvard were working?

Back at the lab, Astrid's working on the code, and Walter brings her an avocado, cucumber and cheese sandwich (with potato chips for the crunch), which is what he developed when the CIA asked him for the best sandwich for clarity of thought. Is it invalid since he wound up in a mental hospital? Astrid's frustrated because she can't see the pattern in the numbers. Walter says, "To break the code, you would have to think like they did, and they lived millions and millions of years ago," adding that they think so differently that their concept of time is all bunged up, as evidenced by one of their months having nine days. And that's the trigger Astrid needs to go all Beautiful Mind and start writing numbers down while Walter reads out the numbers in the first people's calendar to her. She thinks that what they're missing is the cipher matrix, "our decoder ring." Walter continues to rattle off numbers, but there are only so many ways you can make bingo exciting, so we're going to check in on Fauxlivia, who is knocking on an apartment door that is answered by -- naturally -- Feller. "We got a problem," she says. He lets her in to his sleek, ultra-modern open-concept apartment. "The Secretary said we weren't supposed to meet," he says, and Fauxlivia says the Secretary can't see every turn of events. She tells him Fringe found the Polish transistor and are tracking him: "You were sloppy. You've jeopardized the mission," she says, and he gets a bag together -- packing to leave? -- and says he's got to upload another post tomorrow. Interestingly, Fauxlivia tells him he's done enough: "We've got their attention. There's no need to hurt any more innocent people," but Feller's all "all's fair in love and war," which is apparently not a phrase they have on the other side but one that he's learned over here. "If they were in our shoes, they would do exactly what we're doing," he says. We know that Fauxlivia's starting to realize that's not the case, but her phone rings, so she silences Feller with her hand. It's Broyles, giving her an address for Feller and telling her they're on their way with backup." After she hangs up, she tells Feller that they're coming. "Where should I go? Do you have any information on my next mission?" he says. "Yeah, I do," says Fauxlivia, calmly. So you know he's dead. This is why I try to avoid the next-episode previews so that I don't know that what comes next, as Broyles and Peter arrive, noticing Olivia's car already there, is Feller flying out the window and plunge to his death (preceded by a gunshot that made everyone look up). The look on Broyles' face as Feller cracks the pavement right next to him kills me. It's less surprise and more disgusted/pissed. Mercury spatters out of Feller's nose and spreads in a reflective pool under his head. "It's a shapeshifter," he says.