This episode follows the aftermath of Peter entering and activating the doomsday device. He finds himself 15 years in the future; though the device has destroyed the parallel universe, his universe is nevertheless gradually disintegrating. Peter comes to realize the background of the doomsday device and wakes up in 2011. After getting the two universes to agree to work together, he inexplicably disappears.
This episode's glyphs spell:
Peter disappeared from existence after bridging both universes.
Ten Observers can be seen on Liberty Island after Peter is erased.
The ID number "2026" on the squad car in 'The Last Sam Weiss' foreshadows Peter's experiences in the year 2026 in 'The Day We Died'.
Painted text in a parking space in 'The Day We Died' says "ONLY SEPT". In 'Neither Here Nor There' Peter's fate is once again in September's hands as he's the only Observer who has any desire to prevent Peter from being fully erased.
Roughly 15 years later Ella was a Fringe agent.
In "The Day We Died" Peter used the Machine to rip holes in both universes and bridge them together.
In "The Day We Died" Peter explained that the Fringe team from 2026 sent the pieces of The Machine to the past, explaining how there could be technology broadcasting radio signals before the radio was invented.
In "The Day We Died" Peter revealed that the person responsible for the drawings and The Machine was Walter himself.