This episode is set in 2036 where the Observers have taken control of human society. Two FBI agents fight to free their world of the Observers by finding the amber-encased bodies of the original Fringe team who they hope will have a plan to save humanity.
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This episode's glyphs spell:
These glyphs foreshadow the earthquakes generated by Cortexiphan subjects in the next episode.
Observers are featured in this episode.
The security shack on one of the Liberty Island piers in 'The Consultant' says "CHECKPOINT 20-36", foreshadowing 'Letters of Transit' taking place in the year 2036.
A flyer outside the nightclub in 'Letters of Transit' says "Experience the Epicenter Club", foreshadowing the earthquakes caused by Cortexiphan subjects in 'Worlds Apart'.
This is a reference to the ability to interrogate someone's mind after they have died, which both Walter and Nina mentioned in "Pilot".
The Observers have invaded Earth in 2015 in "Letters of Transit". (Image 1)
We later learn in "Letters of Transit" that the Observers and their tech are from the year 2609.
In "Letters of Transit", which takes place chronologically in the future, Olivia isn't present; only Peter, Astrid, and Walter are featured.
The Beacon helps Observers find our world. The Beacon's appearance in "The Arrival" may have been a test or preparation for the future Observer invasion as seen in "Letters of Transit".
Bell tried to use Olivia's powers to create a new universe in "Brave New World (Part 2)".