As unimaginable events continued to unfold, the Fringe Division's investigations often lead them to the important science and technological corporation Massive Dynamic and its enigmatic chief executive, NINA SHARP (Blair Brown). Olivia discovered that she was a test subject of Dr. Bishop and Massive Dynamic's elusive founder and chairman WILLIAM BELL (guest star Leonard Nimoy) as a child. When she uncovered this, she learned of a parallel universe and discovered her ability to detect anything from this alternate world. Shockingly, it was eventually revealed that Walter kidnapped Peter as a child from "over there" after his Peter died, thus creating an imbalance between the two universes.

As life in these two interconnected worlds was explored, complications quickly began to ripple. Peter's romance with alternate Olivia resulted in a baby, and the DNA from this child allowed alternate Walter to activate a "doomsday device" - a device he believed would destroy our world in order to save his. Ultimately, Peter used this device to build a bridge between the two worlds and sacrificed himself in the process.

Season Four will reset the show's contentious context as the Fringe teams must work together to heal their worlds, and solve cases in both. This season will examine the consequences of our heroes' actions in Season Three. Peter saved the day. But in the process, he ceased to exist. His influence on our characters' lives never happened. So what now?