Sacrifices will be made and both universes may never be the same again after Walter and Olivia visit the “other side”.
A shape-shifting embryo is discovered; Peter shares a family secret with Olivia.
A perfectly healthy woman inexplicably dies; Olivia tries to keep Walter’s secret from Peter.
When the sole survivor of a building demolished by an earthquake in downtown Manhattan proves to be from the other Earth, Walter leads the team to Jacksonville, the source of a related experiment that he and William conducted years ago. Now only Olivia and the secrets of her past can prevent another catastrophe.