Just one week after Peter Bishop saved the day and was then wiped from existence, the truce between the two worlds remains intact and the two sides are forced to work together. Lincoln Lee joins the Fringe team as they investigate a shapeshifter case that is very personal to him.

As the victims of a highly intelligent serial killer "Over There" stack up, the Fringe Division "Over Here" is asked to assist. As the two sides tangle and innocent people remain at risk, the suspect's doppelganger "Over Here," a professor who teaches Forensic Psychology, is brought into the fold and forces the team to consider the notion of sending civilians to the other side

Two young bullies are found dead and in just a few hours they rot to an advanced state of decomposition. The Fringe team investigates and uncovers an amorphous figure claiming more victims. Walter becomes increasingly distracted with his mental state.

Olivia uncovers a dangerous force that may be connected to past experiments with Cortexiphan. The investigation forces Walter to leave the lab for the first time in years and travel to Massive Dynamic to examine old case files. Walter struggles with his emotional state as he confronts the demons of his past.

Olivia and the others of Fringe division attempt to determine the origin of Peter Bishop, who purports himself as Walter's son who had died as a young boy in the original time line.

The Fringe team must find the pattern between tragic time loop anomalies. As the investigation unfolds, Raymond, an electrical engineer, and his wife Kate, a professor of theoretical physics, enter the picture.

When a man mysteriously dies by an invisible force, his body rapidly begins turning ghostly white. The Fringe team learns that this is not an isolated incident, and there’s evidence that links the predator to someone who passed away with an unknown genetic disorder. Meanwhile, Olivia suffers from migraines.

In an effort to find a way home, Peter journeys to the Other Side to confront Walternate. However, his venture proves more dangerous than expected. Meanwhile, Olivia receives a dire premonition from an Observer.

Peter's visit to the other side intensifies as the alternate FRINGE division faces off against a formidable new foe in a harrowing race against time.

Olivia continues to cope with the ominous warning from the Observers, while Peter and the team track a girl with the mysterious ability to predict death.

Over Here Astrid gets an unexpected visit from her Alternate, while Peter and Olivia track a killer using a toxin that has yet to be invented. Both universes collide in a case that pushes the boundaries of what is possible.

Peter, Olivia and Walter come face to face with a mysterious and terrifying Fringe event as they get trapped in a town that there’s no escaping from.

As the Fringe team investigates a mentally ill patient who appears to be connected to a series of murders, frightening clues and connections are uncovered that lead Olivia to some shocking revelations.

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.

Following the recent shocking revelations and emotional events, Peter weighs his options as the Fringe team investigates a killer targeting love.

The Fringe team faces a case that appears familiar to Peter. Strangely, it takes place in this timeline.

Lincoln travels to the other side to join forces with Fauxlivia and his own alternate, as they search for a vigilante with a surprising connection to the shapeshifters.

Walter travels to the Alternate Universe to assist in the investigation of a Fringe event with ties to both worlds. Meanwhile, David Robert Jones reveals his next target.

The teams on both sides fight on for a common cause, and there are shocking developments tied to the Cortexiphan children.

Walter is forced to revisit his painful past when a fringe event causes people to spontaneously combust; the team faces off with David Robert Jones.

The Fringe team is pushed to the breaking point as they desperately attempt to prevent a catastrophic event that threatens the lives of everyone.