What appears to be a haunted apartment building claims victims as party goers fall to their death when everyone and their patio furniture seem to fall through the balcony.
Walter thinks our world is starting to crumble as is happening in the other universe, soft spots that could lead to vortexes.
Olivia and Peter kiss, and he glimmers. Olivia is terrified she is incapable of being vulnerable.
An old resident at the apartment building has been causing the sensations because she has been seeing the ghost of her husband. The fabric of the universes is now so thin than she can see through to the other universe and believes she is seeing her husband. Because of Olivia's special relationship with the universes she, too can see him.
Walter thinks the only solution is to begin using amber to stop the soft spots.
The Fringe team theorizes it is caused by people, two couples, one half of which on each side lost the other, somehow breaking through the fabric of the universes because of their deep grief. Peter and Olivia try to talk
Mrs. Merchant into letting go of her husband's doppelganger, to keep from the need to invoke the amber. It works
The rift was also affecting the other side, and another quarantine being investigated by Faulivia and Lincoln was averted.
Olivia and Peter take their relationship to the next level.