Walter, 15 years in the future, indeed knows how to send Peter's mentality back to 2011. Once back in our time, Peter tears holes in both of the universes, creating a bridge so that our main players from each universe - Walternate and Fauxlivia from over there, Walter and Olivia and Broyles from here - are able to meet, converse, and possibly begin to come to terms with each other. To enhance the possibility of this succeeding, the Eternal Bald Observers remove Peter from this bridge, and presumably both universes. Why? Because Peter is the source of the war between the universes - or, more precisely, Walter's taking Peter as a boy from over there to over here. (Possible alternate interpretation: the EBOs are explaining what happened, not what they caused to happen. But my guess is they caused it.)
That's the long and the short of it, I'd say. Next question: how did we get there in tonight's finale?
Well, Peter's mentality seemed in effect to travel from 2011 to 15 years in the future last week. This week, it at first seemed that we were just getting a glimpse of that future, with all of the characters appropriately aged. But, in fact, Walter in that future figures out a way, via Peter in the machine and the wormholes that accompany/cause/are caused by the tears in the universe, to send Peter's future mind back to 2011. And that happened just as Peter connected into the machine in 2011, which resulted in Peter waking up in 2026. So there was time travel going on after all, just more from the future to the past than the present to the future, although they slosh back and forth both ways.
The reason Peter in the future wants to go back to the past is not only to save our deteriorating universe, but do something to make sure Walternate doesn't kill Olivia in the future. Walter, who understands time travel better than any one else on television, explains to Peter that Walter can't go back in time, because he already did what he did (set Peter on the course of activating the machine in 2011), and Walter would not be able to surmount the paradox of going back in time to undo what he did, when what he did is what got him to go back in time ... That's why I love time travel.
But Peter is not so restricted, since he was not the one who set all this in motion, so he - or his mentality - can indeed go back in time.
But now he's apparently no longer in the joint universe that his going back in time created. Because the Eternal Balds removed him.
But where time travel is involved, anything that's done can be undone, as we just saw tonight. And it looks as if Fringe has shifted from a story of alternate realities to one of good old-fashioned, delicious time travel.
See also Death not Death in Fringe
And coming this August ... my essay The Return of 1950s Science Fiction in Fringe in this new anthology ...
5-min podcast review of Fringe
See also Fringe 3.1: The Other Olivia ... Fringe 3.2: Bad Olivia and Peter ... Fringe 3.3: Our/Their Olivia on the Other Side ... Fringe 3.5: Back from Hiatus, Back from the Amber ... Fringe 3.7: Two Universes Still Nearing Collision ... Fringe 3.8: Long Voyages Home ... Fringe 3.10: The Return of the Eternal Bald Observers ... Flowers for Fringenon in Fringe 3.11 ... Fringe 3.12: The Wrong Coffee ... Fringe 3.13: Alternate Fringe ... Fringe 3.14: Amber Here ... Fringe 3.15: Young Peter and Olivia ... Fringe 3.16: Walter and Yoko ... Fringe 3.17: Bell, Olivia, Lee, and the Cow ... Fringe 3.18: Clever Walternate ... Fringe 3.19 meets Inception, The Walking Dead, Tron ... Fringe 3.20: Countdown to Season 3 Finale 1 of 3 ... Fringe 3.21: Ben Frankin, Rimbaldi, and the Future
See also reviews of Season 2: Top Notch Return of Fringe Second Season ... Fringe 2.2 and The Mole People ... Fringe 2.3 and the Human Body as Bomb ... Fringe 2.4 Unfolds and Takes Wing ... Fringe 2.5: Peter in Alternate Reality and Wi-Fi for the Mind ... A Different Stripe of Fringe in 2.6 ... The Kid Who Changed Minds in Fringe 2.7 ... Fringe 2.8: The Eternal Bald Observers ... Fringe 2.9: Walter's Journey ... Fringe 2.10: Walter's Brain, Harry Potter, and Flowers for Algernon ... New Fringe on Monday Night: In Alternate Universe? ... Fringe 2.12: Classic Science Fiction Chiante ... Fringe 2.13: "I Can't Let Peter Die Again" ... Fringe 2.14: Walter's Health, Books, and Father ... Fringe 2.15: I'll Take 'Manhatan' ... Fringe 2.16: Peter's Story ... Fringe 2.17: Will Olivia Tell Peter? ... Fringe 2.18: Strangeness on a Train ... Fringe 2.19: Two Plus Infinity ... Fringe the Noir Musical ... Fringe 2.21: Bring on the Alternates ... Fringe 2.22: Tin Soldiers and Nixon Coming ... Fringe Season 2 Finale: The Switch
See also reviews of Season One Fringe Begins ... Fringe 2 and 3: The Anthology Tightrope ... 4: The Eternal Bald Observer ... 7: A Bullet Can Scramble a Dead Brain's Transmission ... 8. Heroic Walter and Apple Through Steel ... 9. Razor-Tipped Butterflies of the Mind ... 10. Shattered Pieces Come Together Through Space and Times ... 11. A Traitor, a Crimimal, and a Lunatic ... 12, 13, 14: Fringe and Teleportation ... 15: Fringe is Back with Feral Child, Pheromones, and Bald Men ... 17. Fringe in New York, with Oliva as Her Suspect ... 18. Heroes and Villains across Fringe ... Stephen King, Arthur C. Clarke, and Star Trek in Penultimate Fringe ... Fringe Alternate Reality Finale: Science Fiction At Its Best
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