The fate of humanity is on the line as Walter plans to make the ultimate sacrifice to stop the Observers before they were ever created.
To penetrate the Observers' headquarters and rescue Michael, their only hope for victory, Olivia must use her abilities and meet with some old friends.
While Walter tries to learn more about the mysterious Donald after Michael's revelation, Windmark undertakes his own quest for knowledge.
The team joins forces with Nina to recover a key piece of the plan that Walter created to defeat the Observers.
While Olivia and a recently-recovered Peter investigate a mysterious signal coming from a forest, Walter uses LSD to try and recall his memories of his plan to defeat the Observers.
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.
The fight against the Observers intensifies and a Fringe team member plans an attack on his own.
The Fringe team investigates a pocket reality occupying an apartment building, and Peter learns that he has the power to stop the Observers.
Peter takes extreme measures when the team learns of a way to stop the Observers from changing Earth's atmosphere and wiping out humanity.
After infiltrating a subway station to recover a vital piece of Walter's plan, the Fringe team meet up with an old friend... and must determine if he can be trusted.
The Fringe team meets with a group of humans who have taken refuge in the forest and seek to preserve humanity's history any way they can.
After Walter's mind is damaged by Windmark's telepathic probe, the team goes to Walter's old Harvard lab to find the information they need to defeat the Observers.
In the year 2036, Peter, Astrid, Walter, and Etta set out to find Olivia and free her from amber. Once they do, they discover she holds the key to finding the plans for a weapon to defeat the Observers... but Walter is captured and interrogated for the same information.moreless
The Fringe team is pushed to the brink as they try to save every living person from the schemes of Jones' superior.
Walter is forced to relive his past while investigating a series of spontaneous human combustions, while David Robert Jones begins his end game.
The Fringe team on both sides fight a common cause and developments are made regarding the Cortexiphan children.
In the year 2036, a new Fringe team takes on the Observers in a war that will change everything. But to win, they must resurrect a legendary figure from their past, someone who holds the secret to defeating the Observers once and for all.moreless
While David Robert Jones goes after his next target, Walter visits the Other Side to help the team's counterparts with an investigation into a Fringe case that touches on both worlds.
Lincoln teams up with the Other Side and together they investigate a vigilante with a connection to the shapeshifters.
The team investigates a case involving a bizarre mutation that Peter solved in his original timeline four years ago.
While Peter and Olivia deal with the emotional consequences of the Observer's revelations to Peter about his future, the Fringe team investigates the case of a killer who seems intent on murdering... love.moreless
The dying Observer comes to see Walter and Peter, who must take extreme measures to learn what secrets he hides and determine if he knows where Olivia is. Meanwhile, David Robert Jones tries to force Olivia to use her cortexiphan abilities by torturing Nina.moreless
While trying to cope with a new set of memories, Olivia discovers that a mentally ill patient who is a suspect in a string of murders may be connected to her own past. Meanwhile, Walter travels to the Other Side to discover the cause of Olivia's problems.moreless
Olivia, Peter, and Walter visit the town of Westfield to investigate a report of Fringe activity, and discover that they are trapped.
While Peter and Olivia investigate murders involving an inexplicable toxin, Astrid and her Other Side counterpart meet for the first time.