Picking up from the events depicted in last season's flash-forward episode "Letters of Transit," the seemingly peaceful "Observers" seized control of the universe in 2015. Now in 2036, they have become ruthless rulers who will reign supreme. What awaits in the future is the Fringe team's final stand, which will bring together all that they have witnessed in preparation to battle and protect the world.
Set in Boston, the FBI's Fringe Division started when Special Agent OLIVIA DUNHAM (Anna Torv) enlisted institutionalized "fringe" scientist WALTER BISHOP (John Noble) and his globe-trotting, jack-of-all-trades son, PETER (Joshua Jackson), to help in an investigation of an airline disaster that defied human logic. After the defining case was solved and furthermore revealed to be one of a series of unusual incidents linked together, the unlikely trio - supervised by Special Agent PHILLIP BROYLES (Lance Reddick) and assisted by ASTRID FARNSWORTH (Jasika Nicole) - was formed.
As unimaginable events continued to unfold, the Fringe Division's investigations often led them to science and technological corporation Massive Dynamic and its enigmatic chief executive, NINA SHARP (Blair Brown). It was revealed that Walter and Massive Dynamic's elusive founder and chairman WILLIAM BELL (guest star Leonard Nimoy) once were scientific partners, and had used Olivia as a test subject when she was a child.
Through the Fringe team's investigations, Olivia learned that the root cause of these strange occurrences was due to the existence of a parallel universe. Even more shocking was the discovery that Walter had kidnapped Peter as a child from "over there" after his Peter had died, thus creating an imbalance between the two universes that threatened to tear both worlds apart.
Complications in these two separate, yet interconnected, worlds quickly began to ripple throughout each universe. Ultimately, Peter realized his kidnapping was the cause for the alternate world's impending doom. So he chose to sacrifice himself by activating a device that saved the universe, bridged the two worlds together but erased him from existence.
Season Four found the Fringe Divisions working together to rebuild the alternate universe. Despite Peter's seemingly permanent sacrifice, he returned very much alive and helped stop William Bell's mad plans to collapse the two worlds together. Then, after Olivia learned she was pregnant with Peter's child and all seemed right with the world(s), Walter received an ominous warning that "they" were coming.
