Determined to retrieve the plan to defeat the Observers from his memory, Walter tries again with the Thought Unifier, but it just makes him talk nonsense and speak in Portuguese and Swedish. Olivia suggests that because Walter typically documents everything, he may have written it down. But even if files exist, they can't go back to the old Harvard lab, because the Observers have made the university a "No-Go Zone."
Remembering the steam tunnels that run under Harvard, Walter sneaks in with Astrid, Olivia, Peter, and Etta. A section of the lab has been ambered, and Walter's Betamax video recorder sits just inside it. Walter decides he may have made a video instead of writing anything down.
When Loyalist officer Gale Manfretti unexpectedly enters the lab, Etta captures him. Olivia later figures out he just wanted to feed the pigeons.
Walter can jury-rig a laser to melt the amber and free the camera, but they need electricity. Astrid says the campus substation was in the science building.
Etta questions Manfretti about the science building, using a device that ages a person many years in a few seconds. It's Observer tech that the Loyalists adapted to use on the resistance. The torture bothers Olivia, but Etta says Manfretti doesn't deserve sympathy. The Observers have brought war -- and they're losing.
Walter asks Etta for her necklace. They need the silver for solder. She hands over the chain but keeps a silver pellet.
Privately, Olivia agrees that if Manfretti cooperates, she'll tell his son he's never coming home and that he loved him very much. He says the science building contains the main power grid, but rumor has it the Observers use it for experiments "on everything." He gives them his access code, and Walter fashions a substitute for Manfretti's eye from a preserved pig's eyeball, so Peter and Etta can fool the scanner.
Manfretti tells Olivia he joined the Loyalists after a resistance action killed his oldest son. He thinks humans have no chance, and if the resistance stopped fighting, the world would be safer. Olivia says they have to win, so that everyone who died didn't die for nothing.
In the science building, Etta sees a lab where Simon Foster's apparently still functioning head is attached to a machine. She pulls her gun, but Peter stops her. He promises that one day the Observers will pay for what they've done. But not now. They reroute power to Walter's lab and return.
The camera is retrieved, and Etta prepares to take Manfretti to the resistance. Olivia is uncomfortable, knowing he will die. Etta says he doesn't have a son; he lied in hopes that Olivia would free him. Olivia says she sees what the Observers brought to Etta's world. But she's more concerned about what they've taken away.
At a remote location, Manfretti admits that Etta was right: He doesn't have a son. He became a Loyalist because he's a coward. When Etta lets him go anyway, he vows to join the resistance. Something in Olivia's eyes made him feel, for the first time, that the humans are supposed to win. Etta's letting him live because she saw something in Olivia's eyes too: pity, for all of them.
At Harvard, the team watches the video. It shows Walter explaining that the parts of the plan are documented on a series of videotapes. Once all are recovered, they'll know how to get rid of the Observers.
Etta calls Olivia on her comm device and shows her Manfretti walking away.
Videotaped Walter says they must follow the tapes, and begin the journey right away. "You are humanity's only hope."