At Harvard, the team contacts Anil to try and find Michael. Astrid is unable to track the convoy transporting the boy while Walter complains that they have to wait for Donald. Olivia calls Broyles, who is at Fringe headquarters. He questions a lieutenant about Michael's location, claiming he was ordered to provide increased security. The lieutenant informs him that there's a chance in security protocol due to recent infiltrations. Broyles finally convinces him that the detainee is being held at Liberty Island and leaves.
At Liberty Island, Windmark visits Michael in the lab where the boy is strapped to a chair. The captain admits that he is intrigued by him and suggests that the boy communicate with him. When Michael says nothing, Windmark asks why the Fringe team wanted him and still receives no answer. The captain hears a humming build up in his mind but ignores it and asks Michael about September. The boy still doesn't answer and Windmark's nose starts bleeding. He wipes the blood away and repeats his questions, and blood fills his eye sockets. Realizing he's getting nowhere, Windmark tells his men to run diagnostics and found out what Michael is.
Broyles goes to a park and calls Peter on a scrambled line. He tells him where Michael is being held and sends him a schematic, warning them that it's a fortress. When Broyles explains that it's impenetrable, Olivia suggests that they bypass the security entirely by her traveling to the Other Side, finding a safe spot in the other world, and then crossing back over inside of the fortress. When Astrid points out that the cortexiphan burned out of her system, Olivia says that they may be able to get it back and Walter agrees.
The team goes down to the storage area to recover some of Walter's stock of cortexiphan. Walter believes that Olivia's neural pathways can be reactivated temporarily with a dose of cortexiphan, but admits that he doesn't know how long or what dosage is necessary. Peter points out that the side effects could hurt or kill Olivia and refuses to let her try, but Olivia points out that they're out of options. When Peter wonders if they know if the Other Side is safe, Astrid suggests that they use the dimensional window to find out.
The Observer scientist gives Michael a paralytic to keep him still. As Windmark watches, his nose continues bleeding and the captain tells the scientist to tell him when he has results as he walks out.
The team drives to Battery Park and waits until they're alone. Once they are alone, Walter activates the dimension window. They catch glimpses of people on the Other Side and the Statue of Liberty, intact, and realize that their plan has a chance of working.
Donald enters the Harvard lab via the air vents and discovers that no one is there. He goes to work with crystals that he's gathered, distilling a liquid and sealing it in a glass cylinder.
The team meets with the resistance at a safehouse and the field surgeon, Tobin, provides them with what equipment that they have. Walter injects the cortexiphan into Olivia's brainstem and her life signs go up. She tells them to keep going and Walter gives her another injection. Tobin warns them that her life signs are going dangerously high but Walter insists that he's the authority and gives Olivia a third injection. Peter tells his father to stop but Walter says that they need four injections because she will have to cross over four times. He asks Peter to trust him and gives Olivia the fourth injection.
The Observer scientist analyzes Michael's scan and discovers that his neural system has enhanced his emotional responses. His associate goes to inform Windmark.
Peter, Astrid, and Walter watch over Olivia as she sleeps. Walter and Peter realize that they've both made sacrifices and Walter hesitates, knowing he will have to die to complete the plan ... and then tells Peter that he's strong. Meanwhile, Olivia is dreaming of her experience with Etta. Walter wakes her up and she sees them phasing in and out as her vision shifts between worlds. When she wonders how long she has, Walter warns her that she'll have no more than three hours. With each jump, the drug will be burned up and if too much burns up, she'll suffer withdrawal symptoms. If that occurs, Olivia has to cross back immediately.
The team drives to an alleyway near where Fringe Division would be in the Other Side. As Peter walks his wife there, he assures Olivia that she'll make it back with Michael for Etta's sake. They kiss and then Olivia concentrates and makes the first transition.
At Fringe Division, an observation team detects the breach. Olivia goes to Fringe Division and a squad comes out to take her into custody. Fauxlivia and Lincoln are soon notified and meet Olivia in their office. When they go in, they find her looking at a photo of the two of them together with their son. Olivia explains that she looks twenty-one years younger because she was in amber and her counterpart hugs her. Lincoln hugs her after a moment and Olivia says that she needs her help. As they talk about what happened, Olivia briefly hallucinates seeing a young Etta. She checks her watch and confirms she has two hours left, and Lincoln prepares the transport to Liberty Island. Meanwhile, Fauxlivia asks if her other self is okay and Olivia assures her that she is.
Donald continues constructing the time travel device, inserting more vials of the distilled liquid. He finally activates it and confirms that it's working as planned. However, the energy levels drop after a moment and stabilize at a much lower level, and then fade out entirely.
In 2609, Windmark reports to the Commander that Michael has developed an intellect more advanced than theirs and emotional responses greater than humans. The captain grows increasingly disturbed as he suggests that the resistance plans to use Michael to destroy them. He advises the Commander to order the child's death, but the Commander says what is important is understanding what Michael is. He tells Windmark to disassemble it and analyze the pieces.
At the Defense Department headquarters on the Other Side, Fauxlivia checks on the schematics while Lincoln talks about how Walternate is still lecturing at Harvard. He hesitates and Olivia says that they both made their choices and she made no regrets. She assures him he deserves all the happiness that he got. Fauxlivia takes her to the proper room that corresponds to where Michael is being held in Olivia's universe and she makes the second transition. There's no sign of Michael but his brain scans are still up on the monitors.
Loyalist guards take Michael to an operating theater and the doctors prepare to dissect him. Meanwhile, Oliver makes her way down the halls, her vision overlapping between the two worlds. She sees what appears to be an Observer and manages to shoot him despite the overlapping perceptions. Olivia then makes it to the security monitor room, kills the guard, and finds Michael's location on the screens. As she goes to the operating room, an Observer finds her and knocks her down. The lights flash and Olivia knocks the distracted Observer down, gets her gun, and shoots him as the alarms go off.
An Observer teleports into the operating room and tells the doctor to remain there because of the breach in security. Olivia barges in a second later, shoots the doctor dead, and helps a smiling Michael up. The Observer returns and Olivia shifts dimensions. After a moment, the Observer disappears as well, transitioning to the Other Side. He attacks Olivia but Fauxlivia and Lincoln kill him and a second one who follows. Lincoln remains behind to cover their escape and Fauxlivia takes Olivia and Michael to Battery Park. Fauxlivia wishes them well and steps back, and Olivia makes the fourth and final transition. They get Michael into the van and drive away.
Windmark is busy writing in a notebook when his Observers escort the lieutenant in. The captain points out that he was one of three people who knew where Michael was being kept and asked who he told. The lieutenant admits that Broyles claimed he had authorization.
Donald goes to see the Observer known as December and tells him that he needs his former colleague to do. He reminds December that he owes him and December lets him in.