The episode starts with a scene where we see Peter in the future, apparently in the year 2026. This of course was possible after Peter enters the doomsday machine in the episode prior with Olivias assistance & is (so far unexplained) launched into the future to see what the actions of the past create. In this episode we see many characters older, this includes Olivia Dunham's niece, all grown up (played by Emily Meade) & following in her aunts footsteps as a rookie FBI agent. Broyles has moved on to become a Senator. Astrid is now a field agent with the FBI. While Peter, is now a member of our worlds seemingly created Fringe division. A group called "End of Dayers" is trying to speed up the process of destroying the world as a terrorist simply known as Moreau (played by Brad Dourif) attacks places based on "soft spots" that will create more vortexes.
In 2026, our world is still alive, but barely. The alternate universe was destroyed in the battle between the worlds. One notable survivor from "over there" was Walternate however, who apparently came over to our world prior to his worlds destruction. All the key members of our world still appear to be alive in 2026, but with Walternate's world destroyed, he is on a quest to destroy our world & make his son Peter suffer as he has, by taking away what he cares for more than anything, his now wife Olivia. While the FBI & Fringe division work on trying to stop more attacks by the terrorist group, Walternate lures Peter to their old home. Once there Peter discusses with Walternate all thats happened & hopes to convince him to stop. When Peter realizes rationalizing wont work, he tells his father he wants him to come with him or he will arrest him. It is then that Walternate shows his son it was all a trick. Walternates image was nothing but a holographic projection. Meanwhile in Central Park, Walternate is actually there & is about to take the next step in his plan, getting revenge thru killing Olivia. Walternate eventually succeeds in killing Olivia in the future & a funeral is held for her, where all the members you expect to see in our world are at the service.
The loss of Olivia hurts deep for Peter, and it is left to Walter to figure out how to avoid the inevetable destruction of our universe. Walter realizes that the doomsday device was created by himself as a warning sign, so Peter could see what the future would bring if the current path was followed. Walter theorized he went back in time & planted it to be found in the future. Its implied the lore of "The First People" was infact created by him & other trusted members of the group.
With the knowledge of this now in Peters mind, he returns to the present with 1 goal, to merge the two worlds together, with 1 sole purpose....to avoid the destruction of both worlds. When he comes to, he finds Olivia, alive & well, and realizes he must merge the two worlds to work together. As Walter & Walternate, as well as Olivia & Faulivia face each other in our world, Peter explains they must work together, then vanishes.
Neither side shows even a shred of concern that Peter has vanished into thin air, despite all 4 parties there clearly having deep ties to him. Outside the Statue Of Liberty, a group of Observers is seem staring at a bright greet SOL & explaining that they should not remember Peter, as he never actually existed.
With that, the season ends & many questions for next season are created.
The most glaring is- Does this mean the end for Peter Bishop (aka- Josh Jackson) on the show?? Of course, fans will theorize all summer about the meaning of all this & whether or not Jackson will or wont return to the show.
An article that you can read in full here http://bit.ly/l9Kwrd with executive producers Jeff Pinkner & JH Wyman clearly states Josh will be back to reprise the role of Peter Bishop...how that will play out, clearly was not stated however.
Some other questions I think need answering are...
If Peter doesnt exist & seemingly never did, does Fauxlivias baby no longer exist either??
Can Walter & Walternate work together?
Will Olivia or Fauxlivia ever remember Peter somehow?
With the mission seemingly accomplished to save the worlds, what can a new season have in store??
How will they write Peter back in?
With the knowledge now that time travel is theoretically possible in this world, will this lead to other time travel based storylines down the road & how will that affect current world situations?
While I generally dislike the idea of leaving major characters "in limbo" for cliffhangers, thie fact the producers came right out & went "dont panic, Josh is still on salary" quells that considerably. Usually these concerns are over contract squabbles, this seems to simply be more of a logistics issue. When you are dealign with a show where simple logic is continually bent, warped or downright discarded, this is nothing more than a minor blip for bringing him back. Reality is he will be back, just when & how is the question.
Only thing known about the 4th season so far, is that Josh Jackson is eventually going to return. Outside of that fact, nothing is easy to predict. Which is just the way the writers for the hit show like it, keepign the audience guessing.....and for the rest of the summer & perhaps well into next year, they certainly will do just that.