The fourth season of the American science fiction television series Fringe premiered on Fox on September 23, 2011, and concluded on May 11, 2012, consisting of 22 episodes.
[1] Lead actors Anna Torv, John Noble, and Joshua Jackson reprised their roles as FBI agent Olivia Dunham and the father-son duo Walter and Peter Bishop.
The season follows the truce between the two inextricable universes through a bridge Peter created after his consciousness was driven forward fifteen years to make a different choice in activating the doomsday device, as seen in the third-season finale.
Criticisms toward the season were pacing issues in its first-half, unanswered questions regarding strong similarities in established history despite Peter's absence, and lack of answers.
After making use of the Wave Form Device to create a bridge between the two universes, Peter's actions have led to a timeline drastically different than the Observers desire.
However, as he spends time with the Fringe team, Olivia starts to gain memories of the original timeline, and though both are initially worried about this effect, allow it to continue on, rediscovering their romance from before.
Their first action is to disable the bridge created by the Wave Form Device, believing this enables the simultaneous events, but this proves ineffective.
Lincoln Lee, following the death of his long-time partner and the recent changes in Olivia's memories that have caused her to forget her romantic meetings with him, struggles to find his place in the Fringe team.
[29] The producers stated they would continue to employ the use of flashbacks episodes as they "deepened the emotions of these characters", using these as well as flash-forwards "if it suits the story and the things we are trying to get across".
[30] Pinkner and Wyman also stated that they viewed the premiere episode of the fourth season "like a new pilot" to draw in viewers who wanted to watch the show but did not know when to start.
[31] Actor John Noble later clarified that this approach can be used "to unravel some of that mythology a bit" to explain the impact of the disappearance of Peter to new viewers.
[32] Despite the apparent disappearance of his character, Joshua Jackson remained as a main cast member and his commitment to a full fourth season was confirmed.
[33] This fact was played with at the 2011 San Diego Comic-Con where the Fringe cast appeared for a panel; a teaser video showed fake auditions for the open role of Peter, and included cameo appearances by Michael Emerson, Zachary Quinto, Greg Grunberg, Jorge Garcia, Danny Pudi, and Jeff Probst and concluded with Jackson himself dressed as an Observer.
[33] After September allowed Peter to drown, Elizabeth Bishop (Orla Brady) immediately committed suicide fifteen years earlier (mentioned in "The Man from the Other Side") in 1985 from the grief of losing her son twice (altered in "Back to Where You've Never Been").
Walter hated Nina Sharp (Blair Brown) for the next 26 years; he blamed her for breaking the vial with the cure for Peter's disease—ultimately leading to the kidnapping and Peter's death ("Subject 9"); her subsequent guilt led her to gain guardianship of the Dunham sisters after Marilyn (Amy Madigan) died of cancer when Olivia and Rachel (Ari Graynor) were due to go into foster care ("Novation").
Following this, Olivia took on some of Nina's hobbies like horseback riding (seen in "The Cure") in her teenage years (seen in "Novation" and "Forced Perspective") while Rachel still met Greg and gave birth to Ella (Lily Pilblad), though their marriage remained intact and they had a second child named Eddie ("Nothing As It Seems").
("Back to Where You've Never Been") Fauxlivia still took her place, as seen previously ("Over There: Part 2"), though Colonel Broyles never died as Olivia's brainwashing or Cortexiphan experiments were never conducted on her ("Entrada").
These events only occurred when Walternate became aware of her abilities from the Peter-influenced confession she made as a child ("Subject 13"), leaving the cases she solved in the parallel universe unresolved, such as predictive criminal Milo Stanfield (Michael Eklund).
Another difference is Lincoln Lee (Seth Gabel)'s father is alive, after being previously being mentioned to have recently died in his first appearance ("Over There: Part 1").
("Making Angels") "Back to Where You've Never Been" reveals Olivia is unaware of her ability to cross over (as initial experiments to try and send Peter home in 1986 never happened), also revealing she never sought treatment after her car accident from bowling alley attendant Sam Weiss (Kevin Corrigan), and as confirmed in the season five episode "Black Blotter", Olivia never met him in the alternate timeline.
"One Night in October" reveals Fauxlivia still lived with her boyfriend Frank (Philip Winchester) who had broken up with her after discovering she was pregnant with Peter's child ("Immortality"), though they later separated in the new timeline for undisclosed reasons ("The Consultant").
Sally Clark (Pascale Hutton) and Nick Lane (David Call) are alive, having never crossed over to rescue Peter ("Worlds Apart"), but Lincoln was still blown up ("Everything In Its Right Place"), presumably due to a superhearing Olivia ("Night of Desirable Objects")'s absence to alert them of the bomb during Joshua Rose (Shawn Ashmore)'s apartment explosion ("Amber 31422").
Olivia also never met any Cortexiphan subjects as an adult until Cameron (Chadwick Boseman), meaning Nick was recruited by Jones earlier in the timeline than the events of "Bad Dreams".
The website's critical consensus reads, "A daring reset may baffle casual viewers, but those already enthralled by Fringe's knotty mythology will likely become even more invested.
I know this season's timeline switcheroo has alienated some viewers, but even when the show veers off into mythology complexities that start to give me the megrims, I keep faith that Fringe is going to bring it back to the heart of what matters.