Astrid liberates another Betamax videotape from the amber in the Harvard lab. It's not the first in the series documenting Walter's plan to defeat the Observers; it's the fourth. On it, the videotaped Walter munches a Grape Vine (when did he switch to grape?). He says this tape explains a crucial element they will need and gives coordinates in rural northern Pennsylvania that the living Walter doesn't recognize.
Astrid stays behind to extract information from the wonky tape. In the Pennsylvania woods, Etta confides in Olivia that she used to imagine going on missions with her, but now finds that Olivia is so much more than she expected.
Suddenly they're surrounded by humans with severe, bark-like scabbing on their skin. Their leader, Edwin Massey, knows Walter, Peter, and Olivia from the secret library of holographic data cubes his people are keeping. Started by his father, the library records every major historical event from the day of the invasion onward.
Edwin explains they noticed the skin condition after settling there: small patches at first, spreading over time. The Fringe team should leave, unless they want to develop it too. Walter says he has to stay to obtain something from this area, something needed for his plan to defeat the Observers.
Edwin's young son, River, knows about the Fringe team too. He's even made comic books about them, which he shows to Etta, Olivia, and Peter, calling them the last real heroes.
Walter eventually decides the skin condition is a severe immune reaction to the byproducts of the Observers' atmosphere-changing machinery in Central Park. It's like an extreme kind of psoriasis.
Astrid checks in, reporting that a nearby former gold mine contains red quartz crystals that can produce a powerful energy source. But the immune reaction flares up intensely in anyone who enters the mine, causing immediate paralysis through acceleration of the scabbing.
In New York City, Loyalist officers tell Captain Windmark they've tracked down the Fringe team. But one Loyalist, a resistance member, secretly contacts Etta's friend Anil, who warns her.
Edwin shows the team a hologram: five weeks after the invasion, a man named Donald -- dark-haired, in his late 30s -- gathered several reddish rocks from the mine. He was waiting for a scientist from Boston when he was captured by two invaders. Walter doesn't know, or remember, Donald. He's very puzzled . . . and he and Olivia have developed specks of the skin condition. For now, Walter can remove them.
Olivia privately tells Peter her belief that Etta's disappearance was her punishment for feeling conflicted between motherhood and some other destiny. Peter reassures her and says their family's getting a second chance.
While Walter's building a protective suit so he can retrieve 40 pounds of crystals, Etta tells everyone the Loyalists are tracking them. Walter needs copper, and Edwin says a nearby camp may have some, but he's afraid to help and asks the team to leave so the archive won't be discovered. River is disappointed in his dad. Edwin reconsiders and has an emotional talk with his son about cowards and heroes.
The other camp doesn't have any copper, but Edwin pretends they do, which buys him some time to secretly enter the mine and get the crystals. By sacrificing himself for a better future, the recorder of history has made history.
When Loyalists find the van, the Fringe team has already abandoned it. Peter hot-wires a battered station wagon, and they head into the wastelands with the stereo blaring, Walter wearing wraparound shades and grinning in the backseat.