In the year 2036, Peter, Astrid, Walter, and Peter's daughter Etta seek out to find Olivia, who holds the secret to uncovering the master plan that will allow the rebel fights to defeat the occupying Observer force.
The Fringe team revisits the Harvard lab, now under Observer control, to try to find the information they need as the team fights on in their mission to save the world.
As the rogue Fringe team continues to fight off the oppressive Observers' invasion, unforeseen events lead them into a forest where they encounter a strange subculture of people devoted to recording human history.
The team attempt to recover part of Walter's plan from a subway station and discover that an old friend is risking his life to help them... or is he?
When the team learns of a way to cut off the Observers from their future, Peter interrogates an Observer prisoner while Olivia tries to come to grips with their daughter's death.
Walter discovers that one of his tapes holds the key to defeating the Observers. To obtain it, he must travel to an abandoned apartment building where time and space are compressed. Peter, Olivia, and Astrid follow, and Peter discovers that he may be able to fight the Observers directly.
Peter brings his new powers to bear as he plots out a way to destroy the Observers. Meanwhile, the team meets with Nina and Walter realizes he may be losing the struggle against his old self.
Peter reaps the consequences of spying on an Observer leader. Meanwhile Olivia's search for another tape leads her to a woman who seems to be able to divine the future.
In attempt to recall a plan to defeat the Observers, Walter takes an LSD trip down memory lane. Meanwhile, Peter and Olivia trace a mysterious signal to the woods, where they come upon a grisly scene.
The Fringe team is running out of time to save the world. As Peter, Olivia, Astrid and Walter scramble to tap into a key piece of the puzzle to defeat the Observers, they enlist the aid of Nina Sharp who conjures up a plan.
As time dramatically ticks down toward the end of this acclaimed series, Peter, Olivia and Walter stop at nothing to save the universe from Observer rule. Walter enters the infamous deprivation tank in an attempt to uncover a key piece of information about the mysterious figure, Donald. Meanwhile, Captain Windmark sets out on a revealing mission of his own as long-standing questions are answered.
To rescue Michael, Olivia must travel to the Other Side and meet with old friends so that she can enter the lab and save the boy before he is dissected. Meanwhile, Windmark tries to determine exactly what danger Michael poses to the Observers.
To save the present, the Fringe team must send Michael into the future and stop the Observers from ever being created. To succeed, a father must sacrifice everything.