Peter goes out and watches a street that the Observers are walking on. Using his recently enhanced senses, he focuses on two Observers in a car meeting a third one, Mueller, and taking him for a ride. Peter then steps out into the street and delays the car with the two Observers. They miss meeting Mueller, and Peter calls Alin and says that he needs his help with something.
Peter returns to the lab with supplies and Olivia wonders why he left without her. He says that he didn't want to wake her but Olivia realizes that he didn't sleep himself. Peter assures his wife that he's fine just as two loyalists pull up outside. They check over the outside briefly, see nothing, and go on. Once they leave, Walter and Astrid go back to work and cut another videotape out of the amber.
The team watches tape 5 with Walter's plans, as Walter explains that they will need two of the drill beacons the Observers use. The recorded Walter shows them plans of his lab at Kelvin Genetics and explains that Bell kept two of the drills there and the storage chamber can be unlocked with Bell's hand. Astrid points out that Walter cut off Bell's hand when he was in amber. She also explains that Bell betrayed them to the Observers and Walter has muddled memories of what happened. Peter reminds him that Walter called and summoned them, and they had no choice but to go into the amber when Bell led the Observers to them. They go back to work and start cutting the hand out of the amber
Once they have the hand, they drive to the storage facility, which is buried under rubble. Peter spots the doors with his enhanced senses and then hastily says that he deduced their location using his engineering knowledge. Olivia points out that he's bleeding from one ear. Walter examines it and Olivia suggests that the explosion they caused when they closed the wormhole might have injured him. Meanwhile, Astrid suggests they use an antimatter baton to clear a path against the door. Walter warns against it and suggests that they go through it. Alin calls and Peter takes the call privately. He says that he did everything just like Pete said but Royce never forgot his briefcase in the park and he never had a chance to substitute the one they made. Peter says that it's impossible and says that he will meet him.
As Peter prepares to leave, the others tell Peter that they're going to talk to Nina, who works for the Ministry of Science and can get them access to technology that will let them change the structure of the concrete and clear it. Peter says that he has to meet with Alin for something that Alin wouldn't explain over the comms. Olivia looks intently at him and Peter assures her that there's nothing to worry about.
In Brooklyn, Nina is outside the Ministry of Science when her assistant gives her a letter. Nina tells the assistant that she'll be out of the office for a bit and then goes to the river. Olivia is waiting for her and Nina offers her condolences on Etta's death. She refused to contact them for fear it would endanger their safety, but Olivia says that now they had to meet with her. Nina and Olivia meet with Astrid and Walter, and Nina explains that the Observers have a device that sublimates solid matter into vapor. She tells them to meet her outside the building in ten minutes.
Ten minutes later, Walter pulls up in the van. Nina pulls up and asks if he's mad at her because she showed Simon and Etta how to restore Walter's brain. She insists that they needed Walter fully restored and asks if he's noticed any personality changes, and Walter admits that there have been some. Nina admits that she doesn't see any signs of the old Walter but says that Walter would know better than her. Walter says that this time it's different because Peter won't let him become that man again. Nina's assistant Hastings comes out and is honored to help Walter.
Peter meets Alin in the park and has him go over everything that happened. Much to Alin's surprise, Peter describes everything in detail. Alin says that Royce talked to someone on his comm and Peter realizes he didn't take the variable into account. He sees a new future, takes the briefcase, and gives Alin the address of an Observer precinct. He tells Alin to call him when Royce and Mueller arrive and then hotwires a car. As he does, he moans in pain for a long moment and then gets control of himself.
Peter goes to Cavatina, a restaurant favored by the Observers, and checks the briefcase. The coat check girl takes it and warns Peter to be careful so that he isn't read. Peter tells her to get the phone before it rings, and he dismisses it as a parlor trick. He then goes to the bar, checks the time, and waits.
As Olivia and Astrid wait in the van, Astrid asks how the couple is doing and Olivia says that Peter isn't sleeping and he's always off somewhere. He always has an explanation that makes sense but Olivia is sure there's something that he isn't telling her. Astrid points out that they've both been through a lot but admits that Peter isolated himself after the invasion. However, he's come a long way since then. Olivia figures that they're stronger, but she's worried that she's losing him again.
At the restaurant, Peer watches as Royce comes in and checks his briefcase. Once the Observer sits down, Peter looks at the coat check girl, checks the time, and then walks over to her. She gets a call from her boyfriend and Peter asks for his briefcase. Distracted, Cavatina gives him Royce's briefcase and leaves Peter's behind.
Hastings gives Astrid and Olivia the sublimation equipment and instructs them in how to use them. He warns that a blue light means a malfunction and they need to run. Meanwhile, Nina tells Walter that Peter may not be able to do enough to restrain Walter if he reverts to his original self. She knows that Bell went through the same thing and that her love for him wasn't enough. Bell couldn't let go of the power so he let her go, but Walter arrogantly tells her that Bell never loved anyone by himself. He tells Nina that she should know better and she tells Walter that she just saw Walter's old self. Walter says that he's come a long way and that his love for Peter and vice versa will save him. Nina says that she hopes it's true as Olivia comes over and says that they're ready. She warns them that once they use the technology, the Observers will notice the chance in the atmosphere and arrive within minutes. Nina wishes them good luck and Walter leaves with the others.
Alin watches the Observer building and sees Royce arrive. Mueller arrives a few seconds later, goes upstairs, and meets Royce and another Observer in a briefing room. They open their briefcases and a bomb goes off, causing the flesh on their bodies to slowly melt.
Olivia, Astrid, and Walter return to the ruined building and sets up the pillars for the sublimator. Peter arrives as Alin calls to tell him that his plan was a success and the Observers have gathered there. After Pete tells Alin to go home, he walks over and Olivia asks what happened. Peter claims that Alin set up a meeting but then had to cancel because he was delayed at a checkpoint. Olivia looks at her husband suspiciously as he goes over and Walter explains what he's doing. They activate the device and the rubble vaporizes.
The team goes inside and powers up the security scanner. Walter then places Bell's hand against the scanner and the door opens. Walter goes through Bell's collection, finds an old album of his that Bell stole, and then finds a safe that Bell built for special items. They wonder if they can get in and Walter figures that Bell used the same combination he used on everything. Walter hesitantly tries to unlock the safe without success. Astrid and Olivia warn that the Observers are on their way but Peter tells his father to focus and relax. After a moment, Walter remembers the combination--5, 20, 10--and opens the safe. However, there is nothing inside and Walter figures that Bell was trying to lure him to the Observers. They notice a small metal disk inside, a notebook, and a photograph of Nina.
Peter examines the disk and activates it with his touch. The building shakes and two of the beacon drills emerge from the floor. The team grabs them and heads upstairs, and Peter casually walks out despite Olivia's warning. He tells the others that they should split up and that he'll take his car and go on his own. As they go, Walter tells Olivia that he has to make a stop first.
That night, Walter meets with Nina and tells her that they have the cylinders. He gives her the photo from the safe and explains that Bell kept it in his safe with his most prized possessions. Walter tells Nina that he was wrong and that Bell loved her... and that it still wasn't enough. He asks Nina to take out the pieces of his brain, assuring her that it won't seriously affect him.
Olivia returns to the lab and discovers that Peter has sketched out timelines on the boards. Peter comes in and explains that they're timelines of Windmark's top lieutenants. He accounted for every second of each one's day and used that information to manipulate event. Peter quietly tells his wife that he implanted the Observer tech that gives them their advantage, and he used it to plot their probable futures and make sure that they were in one place. Then he used the flesh-eating toxin from Walter's cold storage to kill them. Olivia realizes that Peter knew that the Observers would be responding to the attack and wouldn't come to the storage site. Olivia says that Peter can't do what he's doing, but Peter speaks in chorus with her, predicting what she's going to say. He tells her that they're going after Windmark next to avenge Etta and starts scribbling out Windmark's timeline as Olivia backs out of the room.
Walter examines one of the cylinders and then the other pieces that they've assembled by following the tape directions. He turns on the radio that was left for them but hears nothing, and then puts on an album. Astrid comes in and assures him that they did good, and kisses him on the cheek as she goes to bed. Walter turns the music up and listens to the lyrics of Bowie's "The Man Who Sold the World."
Peter continues plotting Windmark's timeline, determining the origin point.
Walter lies down and looks up into the darkness.
Peter plots that Windmark is in an elevator.
Windmark takes an elevator out of the building.
Peter scratches at his head and his hair starts coming away.