Olivia manages to escape imprisonment and tries to return to her own universe, only to discover that all possibilities are blocked and her memories are not her own.

Three robbers dig up a mysterious box from a suburban home, but it soon proves deadly to anyone exposed to it... with one exception. The alternate Olivia works with Newton to find the box, while accompanying Peter and Walter as they investigate the deaths. Meanwhile, William Bell's last will and testament is read, and Walter gets a surprising gift.

The Other Side's Fringe Division investigates a mysterious series of bus accidents that resulted in the deaths of specific individuals. Meanwhile, Olivia begins to have mysterious visions of people she finds strangely familiar, and Secretary Bishop tells Colonel Broyles why he has placed an impostor on his team.

A deep-cover shapeshifter is inadvertently exposed, and the Fringe team hopes to probe its body and download critical information about the Other Side's infiltration plans. Bolivia orders Newton to acquire the data, and Newton calls a sleeper agent into play. Meanwhile, Walter adjusts to life as the owner of Massive Dynamic.

When a man frees his twin brother from an amber quarantine zone, Secretary Bishop realizes he must keep the knowledge secret before the public learns that it can be done... at the cost of weakening the quarantine zones. Meanwhile, Olivia agrees to help the DOD test her ability to travel between worlds, and tries to cope with visions of Peter Bishop warning her that something isn't right.

On This Side, Fringe Division investigates fifteen people who were all stricken with retrograde amnesia after hearing a mysterious radio transmission. Meanwhile, Walter disagrees with Peter's experiments on the destruction device.

On the Other Side, a serial kidnapper abducts another in a series of children, all of who have been eventually discovered with massive cellular atrophy. One of the victims is Christopher Broyles... the son of Colonel Broyles. Olivia and her team pursue the case, but Olivia also secretly makes arrangements to get to Liberty Island and find her way back to her world.

Olivia struggles to return to her world and gets help from an unexpected ally. Meanwhile, Bolivia's ruse is uncovered and the race is on as she attempts to return to the Other Side before Peter and the others can catch her.

As Olivia returns to work, the Fringe team is called in to investigate the case of a man who temporarily survived the removal of his heart. While they hunt down the serial organ thief, Olivia deals with the discovery that Peter unwittingly had a romantic relationship with her counterpart.

The Observer contacts Walter and asks for his help in setting the balance straight and rectifying a shared mistake. Meanwhile, a retired musician emerges from obscurity when the staff at his hospital discover that he received a visit from his son... who has been dead 25 years.

The Fringe team discovers the connection between Peter and the world-destroying Machine, and try to determine what it is and how they can control it. Meanwhile, a mysterious assassin stalks the remaining shapeshifters on This Side, an assassin who is always one step ahead of the team.

A trio of ex-soldiers use a chemical that dissolves human bones against the scientists they hold responsible for the plight of their families, and Walter tracks down one of the Cortexiphan suspects to help them find the men before it's too late. Meanwhile, Nina discovers who the author of The First People book is.

On the Other Side, a scientist uses human hosts to develop a new form of skelter beetle to produce a vaccine, unconcerned about the cost in lives. The alternate Olivia and her team hunt the scientist down, and she learns a startling secret about herself.

A woman is haunted by the ghost of her dead husband, but it soon becomes apparent that much more is at stake when partygoers in the same building plummet to their deaths... through a solid stone balcony.

The secrets of the past are revealed, as Walter attempts to use the cortexiphan children to return the Other Side's Peter to his home dimension. Meanwhile, Young Olivia discovers the trigger for her abilities, and the Other Side's Walter realizes what has happened to his son.

The Fringe team is called in to investigate the death of a thief whose corpse defies gravity. Meanwhile, Walter becomes obsessed with bringing William Bell's spirit back so that he can use his friend's help to stop the breakdown of barriers between the two universes.

While investigating reports of a woman that can't be killed, the Fringe team deals with the return of William Bell.

On the Other Side, a mysterious team of doctors abducts Bolivia and attempts to induce childbirth. Lincoln and Charlie race desperately to find her, while learning the truth about their comrade and her recent adventures on This Side.

The team makes a desperate attempt to remove William Bell’s consciousness from Olivia’s body before she’s lost forever.

Source: Fox

The beginning of the end is triggered when Walternate finds a way to wreak havoc “over here."

Source: Fox