In the year 2036 the team searches for Olivia, who has been frozen in amber -- only to lose Walter in the process. When he faces interrogation at the hands of the Observer leader, the only hope for the future could be lost forever.

The team returns to Walter's old lab inside Observer-controlled Harvard in order to retrieve information crucial to the resistance. Olivia sees how far Etta is willing to go after capturing a loyalist soldier.

The first of a set of clues left by Walter in the past sends the Fringe team to a remote forest community, whose residents have committed themselves to maintaining a record of human history.

Peter makes a risky excursion to get a present for Etta, and the team learns that their position inside the lab has been compromised. A brief reunion with Broyles leads to a direct confrontation with Winmark and the Observers.

The Resistance asks the Fringe team for help attacking an inter-dimensional shipping lane used by the Observers, and Peter uses his unique skills to interrogate a captured Observer in the hopes of striking back hard at the enemy.

After retrieving another tape Walter pursues a new lead on his own, winding up in a pocket universe where the same laws of physics do not apply -- and where a crucial piece of the plan to defeat the Observers lies hidden.

The next tape recovered from amber leads the team to Bell's storage facility, but Walter and Olivia must secure help from Nina Sharp in order to gain access. Meanwhile Peter uses his new abilities in an attempt to orchestrate his own fringe event.

Olivia goes in search of a piece of equipment in a remote area, where she meets a woman with a remarkable gift. Peter's crusade against Windmark draws the enemy's attention, and Walter and Astrid try to discern what is happening to his brain.

The team hopes that an incoming radio transmission might lead them to the mysterious Donald. Meanwhile, Walter tries to job his memory with a potent LSD trip.

The team turns to Nina for help in communicating with a child Observer, which puts her in jeopardy with the enemy after Windmark discovers her connection to the Resistance.

Walter's newly-recovered memories lead to a reunion with Donald, who reveals the true nature of the plan to stop the Observers. Elsewhere in time, Captain Windmark discovers the anomaly's connection to a banished Observer.

Facing impenetrable security guarding Michael at Liberty Island, Olivia risks her life to cross to the other universe to bypass the guards. Windmark subjects the boy to tests but gets more than he bargained for.

With the fate of the world hanging in the balance, the Fringe team attempts to execute Walter's plan to alter the future -- as Windmark and the Observers close the noose around them.