Olivia, captured on the other side, attempts to escape and return to her home world. Meanwhile, Walter attempts to reconcile with Peter, but they are both unaware that the Olivia with them is not the real one.

A television drama centered around a female FBI agent who is forced to work with an institutionalized scientist in order to rationalize a brewing storm of unexplained phenomena.

A television drama centered around a female FBI agent who is forced to work with an institutionalized scientist in order to rationalize a brewing storm of unexplained phenomena.

A television drama centered around a female FBI agent who is forced to work with an institutionalized scientist in order to rationalize a brewing storm of unexplained phenomena.

Season 2, Episode 23 - "Over There, Part 2?
Sacrifices will be made and both universes may never be the same again after Walter and Olivia visit the "other side."

Much of Season 2 focuses on the alternate universe. It is established that Peter from the present universe died from a childhood disease; Walter, already with knowledge of the other universe, crossed over hoping to save that Peter, but instead was forced to bring him back to his universe, and kept this knowledge to himself. While Walter was aware that his crossing created "soft spots" in his universe, he is unaware that more significant and dangerous singularities occurred in the alternate universe as ripple effects of his crossing. As a result, the alternate Walter (referred to as "Walternate"), now U.S. Secretary of Defense, leads a more powerful Fringe division in the alternate universe to deal with further breaches, including the development of shapeshifting technology that could travel to the present universe, and the means to communicate with its agents once there. Meanwhile, the Observers warn Walter that he should not let Peter return to the alternate universe as to avert a great disaster to either universe; Bell later describes this "great storm" to Olivia when she arrives.

EP 3.6 : 6955 kHZ
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.