An Enemy of Fate
September implores December to help fix a key component of the device, an initiating reactor, to send Michael to the future, despite knowing this will erase September from time. September appeals to the compassion December, like the others of the original Observer team, developed for the humans. Later, September regroups with Fringe to explain the failing reactor and describe the function of the device: to create a wormhole, using the two Observer cylinders as stabilization points on either end, and the large electromagnet needed to launch the second cylinder into the future of 2167. Once the wormhole is stabilized by the red rocks from the mine, Michael would be sent through, to meet an agent to take him to the Norwegian scientist in order to stop the experiment that would be responsible for creating the Observers. As they discuss this, Olivia is still puzzled over why Michael had willingly let himself be captured and believes he must have expected to be rescued. One additional part is revealed to be necessary to assure the magnet's operation: a synchroscope. Peter begins to dig through the amber in the lab to look for it.Captain Windmark, having discovered Broyles' alliance with the Fringe team, interrogates him about the abduction of Michael from a secured facility, believing him to be "The Dove", a mole for the resistance. Windmark leaves, and Broyles sets off to meet Fringe until he realizes that Windmark intended to follow him to the Fringe team, and keeps his pursuers distracted. Though he tries to elude them, Broyles is captured.
Looking through the amber, Peter finds a tape that is addressed to him in Walter's handwriting. The tape is a goodbye message from Walter to Peter, recorded before they were frozen in amber, and alludes to an envelope that he will receive at some point. Walter in the present explains that he will be the one to travel with Michael into the future, having already inoculated himself in 2015 to do so, and they will be forced to live out their lives there so as to ensure a paradox is not created and that the Observers are wiped out from the point of the original invasion, in 2015. Walter and Peter share an emotional moment, Walter saying he appreciated every minute of the "stolen" time they have had, and calling Peter his "very favorite thing".
Olivia and Astrid go to collect a new initiating reactor from December, but find him hanged and the reactor stolen by other Observer and Loyalist forces. September asserts that there's no technology in 2036 to create the reaction needed. Olivia looks to Michael to gain insight; he motions her to be quiet, during which Astrid comes up with the idea of using one of the Observer shipping lanes as their wormhole. They begin to make plans to take over one of these the next day, when they learn of Broyles' capture from Anil. They set out to retrieve a shipping lane control cube, using many of the past Fringe biological materials to kill several Observers and Loyalists. They obtain the control cube and rescue Broyles along the way.
Meanwhile, Astrid takes Walter to show Gene, the cow, ambered in motionless peace in the lab. Walter and Astrid share an emotional moment with the hope to wake up back in the lab drinking strawberry milkshakes, after all this ends. Walter finally shows his appreciation to Astrid in words, saying she always knew how to soothe him. and adds that her name is beautiful. After this, September reveals to Walter that he has taken the only spare dose of inoculation to take Michael into the future instead of Walter, having come to have paternal feelings for Michael.
The Fringe team races ahead of the Observers to hijack the wormhole and launch one of the Observer Beacons through it. As they get ready for Michael, Windmark arrives and attempts to grab him. September, Peter, and Olivia fight Windmark. Windmark gains the upper hand, but Olivia, under emotional duress, activates her latent Cortexiphan powers. She draws power from the surrounding city, and Olivia psychokinetically smashes Windmark between two cars (this was only possible because Olivia had dosed herself with Cortexiphan in order to save Michael, explaining why Michael allowed himself to be captured, as he knew she would need her Cortexiphan abilities to stop Windmark).
September races to take Michael to the wormhole but is shot and killed by a stray bullet. Walter realizes his fate, and takes Michael through the wormhole as Peter, Olivia, and Astrid look on. Before entering the wormhole, Walter looks back at Peter and Peter mouths "I love you, Dad" to Walter.
Time flashes back to 2015, where Peter, Olivia, and their young daughter Etta are enjoying a day in the park (first seen in the season premiere and also in flashbacks throughout the season). The Observer invasion does not occur, and the happy family returns home. When Peter checks the mail, he finds an envelope addressed to him from W. Bishop, containing only a drawing of a white tulip.
Tropes
- Book Ends: The chaos of the series begins and ends with Walter and a boy stepping through a portal.
- Bittersweet Ending: The Observers are erased from existence, preventing the invasion and all the horrors that resulted from ever happening, but to prevent a paradox, Walter and Michael's 2015 selves are erased from the timeline to allow their 2036 selves to still exist in 2167, meaning Walter's friends and family will never see him again.
- Deader than Dead: Windmark is crushed to death between 2 cars and then moments later is erased from existence when Walter and Michael journey to the future.
- Ret-Gone: The Observers.
- Walter and Michael's 2015 selves also erased from the timeline at the moment the invasion would've occurred to prevent a time paradox, while their 2036 selves reside in 2167.
