In this episode, the Fringe team investigates mysterious deaths at an apartment building, the result of a merging between the prime and parallel universes. While there, they encounter a woman who claims to be able to see the ghost of her deceased husband.
Synopsis provided by the Fandom Wiki, Fringepedia, and Wikipedia.
This episode's glyphs spell:
This fringe event was generated by intense love and grief shared between two people in opposite universes.
The Observer can be seen walking past Chris and Sylvia as they walk to the party.
The license plate of one of the victims in 'Immortality' is "APT6B", foreshadowing the apartment under investigation in '6B'.
The "Tulip Food Store" signage in '6B' foreshadows Olivia and Peter meeting for the first time in a field of tulips in 'Subject 13'.
In "Os" the team learned that Bell had enacted his Soul Magnet plan before death using Olivia as a host.
As Olivia continued to regain her memories in "A Better Human Being" she mentioned remembering the events of "6B".