A young Etta is playing in the park while her parents Olivia and Peter look on. She picks up a dandelion and blows on it, while around her people suddenly start running. Peter looks to his daughter and sees a burst of white light envelop the city behind her. Observers appear out of nowhere and start walking across the park toward Etta, and Peter and Olivia run to get their daughter. The next thing Peter knows, he is in a medical tent and EMTs are tending to Olivia while he tries to find Etta.
In the year 2036, Peter wakes up from his dream and confirms that Walter is nearby, sleeping on the couch of Etta's apartment. When he looks in on Etta, he confirms that she is fine as well. She wakes up and he assures his daughter that he was just checking on her. As he leaves, Etta examines the bullet strung on a necklace around her neck.
Walter wakes up and notices a rainbow light reflected onto the nearby wall. He looks out the window but is unable to see what is reflecting the light.
Peter checks on Astrid, who is in the kitchen playing the newest edition of Scrabble against the computer. Walter comes in and tells them that they have to find Olivia. He explains that Olivia was at an address in New York 21 years ago and on the phone with him when she cut off. Walter tells them that he sent Olivia to Grand Central Station to recover apiece of equipment he needed to assemble the device they need to defeat the Observers. He worked with September, the renegade Observer, who scrambled the knowledge of the components within Walter's mind. A few days after he lost contact with Olivia, Walter was forced to amber himself. As Walter goes to get dressed, Peter assures his daughter that they'll find Olivia if she's still alive.
The Fringe team drives to the address and discovers that the Observers have paved over Central Park and replaced it with one of several machines that are pumping carbon dioxide into the air to convert it to their specifications. A nearby block has been ambered over and they discover that a number of survivors have been cut out. Etta says that amber gypsies took them and they go to a black market. Etta sends Peter and Astrid in since the gypsies know her as a Fringe agent. She gives Peter some walnuts to negotiate with. Peter talks with the amber gypsy in charge and he sends them into the display hall… and triggers a hidden alarm.
While he waits with Etta, Walter talks about how he remembers Etta as a child since only a few months have passed for him since the last time he saw her while he was trapped in the amber. Touched, Etta kisses him on the cheek.
Peter and Astrid don't find Olivia among the amber survivors and talk to the head gypsy. After bribing the man with the walnuts, the gypsy finally gives him the address of the man who bought the amber block containing a woman matching Olivia's description.
Bibliologist Edward Markham is at home watching television and using Olivia's amber block as a dinner table. There's a knock at the door and he insists that his apartment is sanctioned. Peter bursts in and easily disarms Markham when he goes for a gun. Markham is stunned that Peter hasn't aged. When they find the block of amber, Markham explains that he bought it because he loved Olivia since he first saw her and figured that she would fall in love with him once he freed her. As they look for a gurney to get the block out, Markham tells them that he sold everything he had to buy it.
The amber gypsy calls the loyalist hotline and tells them that he has information.
Peter gets the amber block down to Etta's van while Walter admires Markham's collection of books. An Observer teleports in and draws a gun on him, but Etta arrives and shoots him, but another Observer arrives and stuns her. Markham begs the Observer not to kill him, distracting him long enough for Etta to kill him as well. She runs down to the van but discovers that Walter didn't make it there, and they're forced to drive away with Olivia as loyalist troops show up. More of them enter the building and capture Walter as he tries to escape.
Back at the lab, the others free Olivia from the amber and Peter explains what has happened. As Olivia explains that she was forced to amber herself to avoid the Observers, she sees her daughter and Peter introduces her. Olivia tells Etta that she's beautiful and hugs her, and then wonders where Walter is. Peter tells her that he was captured and Olivia shows them the electronic device she recovered from Grand Central Station.
Inspector Windmark has Walter strapped to a chair in an interrogation room and wonders how he's alive. When he tries to read Walter's mind, he discovers that Walter is thinking of music in an attempt to block him. Windmark admits that he finds music interesting but it has no value to the Observers, and Walter says that it helps him see things like hope. Windmark tells him that there is no hope and warns him that if he continues resisting the mind probe then he'll become a vegetable.
Etta takes Olivia, Peter, and Astrid to an underground resistance lab and introduces them to Anil and Klopinski, her fellow agents. They share a toast to a dead comrade, Elias, and then Etta ask Alin for help. Outside, Peter and Olivia wait and she realizes that they failed to save the world again. Peter admits that he had given up on seeing her and that he left her alone when she went to New York because he felt he had to stay in Boston and find Etta. Olivia says that neither one of them were thinking straight after the loss of their daughter but Peter insists that he knew what he was doing and he refused to give up on Etta.
Etta calls them in and Anil explains that Olivia's device is a transilience thought unifier, Model. It doesn't do anything by itself, but it can access the wearer's hidden thought. The unifier doesn't appear to work but Peter figures that they can use it to recover the plans for the anti-Observer device in Walter's mind. They check the security records from their tap into the main feed and spots Walter being taken away from Markham's apartment. Peter warns the others that the Observers may be able to pull the information from his father's mind.
Windmark probes Walter's mind, torturing him as he demands to know who freed him. The Observer realizes that someone has partitioned Walter's mind, protecting the information, and suspects that another Observer was responsible. Windmark continues applying telepathic pressure, surprised that Walter can put up so much of a fight. He admits that he could use a unifier to restore Walter's fractured memories but that it would take time to key it to his biological signature. Windmark finally gets an image of Etta as a young girl, the way that Walter sees her, and wonders what she has to do with Walter's plan. Walter passes out, blood streaming from his nose and ears.
As Etta checks the security footage to find where Walter has been taken, Olivia admires their daughter and Peter admits that seeing Etta is a dream within the nightmare of their lives. She finally determines that Walter has been taken to the Napean Building and Alin admits that they have tech that could get them in. It can cause simulated death in a human being, letting someone bypass the Observer's telepathy. However, Klopinski warns that if they use it now then they'll lose the element of surprise in future. Etta points out that they need Walter to stop the Observers and her fellow agents agree to help.
Later, Amber drives to the Napean Building in a van and tells the loyalist tatties that she has two resistance fighter corpses for Windmark. The leader, who knows Etta from Fringe division, scans the bodies of Elias and Peter and confirms that they're dead. He goes in with Etta and tells her that her superior, Foster, was found embedded in a block of amber next to Bell and believed to be a traitor. He suggests that Etta talk to Windmark, who is eager to discuss the situation with her.
In the interrogation room, Windmark picks up an image of stones and wonders how Walter can understand the physics involved. He continues to telepathically probe, telling him to lower his mental walls.
Etta wheels the corpses into the storage room and then knocks out a tattie as he starts to steal from the bodies. She revives Peter and they go to let Olivia in while Astrid hides in the back of the van. The trio go to the building's temporary atmospheric converter and Peter sabotages it, setting off an alarm.
As Windmark finishes with Walter, he hears the alarm and goes to investigate. Peter and Etta break in and free Walter, who has passed out from the strain. They shoot their way out of the building, rendezvous with Olivia, and get to the van. As they drive away, Olivia provides cover fire and Walter asks Astrid for some music before passing out.
Once things have settled down, Windmark goes over the security footage taken of the intrusion and realizes that Etta is the young girl in Walter's memories.
When the team gets back to Etta's apartment, Walter wakes up and tries the unifier. It activates at his touch but he discovers that he can no longer remember the plan because of mental damage caused by Windmark's telepathic probes. Despairing, Walter walks away, saying he can't do it anymore, and Olivia realizes that the plans have been wiped out. Etta warns that the brain damage will never heal and they can't recover the information and save their world.
Later, Walter tries to sleep but sees the same reflected light from earlier. He goes outside to investigate and discovers that someone has created a makeshift street sculpture out of hanging CDs. Noticing a nearby taxi, Walter gets in and finds more of the CDs along with a player. As he puts in a CD and listens to the music, he sees a dandelion growing through the concrete and smiles.