This episode follows the Fringe team's attempts to extract William Bell from Olivia's brain by entering her mind with the help of LSD.
Synopsis provided by the Fandom Wiki, Fringepedia, and Wikipedia.
This episode's glyphs spell:
The key to rescuing Olivia from the depths of her mind was to first understand her fears and then for her to face and overcome them.
The Observer can be seen at the hospital when Olivia is brought in.
A small, cartoon bird is seen in Chinatown when Fauxlivia escapes captivity in 'Bloodline'. Broyles sees this same bird in 'Lysergic Acid Diethylamide' during his LSD trip.
A poster in Olivia's mind in 'Lysergic Acid Diethylamide' that says "Be Vortex Aware" foreshadows the vortex that consumed part of a ranch in '6:02 AM EST'.
In Olivia's mind in "Lysergic Acid Diethylamide", Nina was outwardly friendly but had murderous intentions when she tried to push Walter down an elevator shaft. (Image 1)
Broyles saw dead Alt Broyles in "Entrada" and it had been haunting him.