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.

The episode was rated 8.20 from 1201 votes.

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 episode was rated 8.24 from 1201 votes.

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.

The episode was rated 8.25 from 1176 votes.

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.

The episode was rated 8.25 from 1171 votes.

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.

The episode was rated 8.28 from 1168 votes.

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.

The episode was rated 8.30 from 1213 votes.

A mysterious Fringe event causing people to spontaneously combust forces Walter to revisit his painful past while the Fringe team faces off against David Robert Jones to save the world, or worlds.

The episode was rated 8.31 from 1228 votes.

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.

The episode was rated 8.31 from 1189 votes.

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 episode was rated 8.32 from 1184 votes.

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

The episode was rated 8.33 from 1186 votes.

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

The episode was rated 8.41 from 1213 votes.

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.

The episode was rated 8.41 from 1221 votes.

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.

The episode was rated 8.45 from 1223 votes.

The Fringe team goes back to the future as the story jumps ahead to 2036, when the Observers and the Fringe team engage in a game-changing battle.

The episode was rated 8.53 from 1350 votes.

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

The episode was rated 8.60 from 1277 votes.