And Those We Left Behind - S4-E6
Plot hole: The very ending scene where Peter (in this version died in the ice as a boy so Walter's wife never met him) takes off some of the dust covers then picks up a toy airplane. The toy airplane he got as a child from ... Walter's wife when she was trying to placate him in an earlier episode for trying to run "home". This toy airplane wouldn't have been his as a child in this version of the universe. (00:42:00)
And Those We Left Behind - S4-E6
Factual error: In the final scene with Peter and Olivia in Walter's campus housing, Peter uncovers items that should have been in the house for years and they are dusty. The last thing he uncovers is a brand new flat screen HDTV with stickers on it, which would not have existed 17 years prior to then, when he was committed to St Clarie's Institution. (00:42:10)
And Those We Left Behind - S4-E6
Continuity mistake: While beginning to take the radiation readings of the Jeep during his time jumps, Peter has a wedding ring on his finger. After cutting away and back again, the wedding ring is no longer on his finger. (00:15:15)
Brave New World: Part 1 - S4-E21
Continuity mistake: This is when Peter and Olivia are discussing different Boston's suburbs as their potential new home. The sun is on the right side of Olivia's face in one shot. In other shots, it isn't.
Brave New World: Part 2 - S4-E22
Continuity mistake: The left side of Peter's face is alternately bathed in sunlight or not throughout the scene when he and Walter talk in front of Olivia's hospital room.
Other mistake: In the scene where Peter and Lincoln are driving to question Daniel Hicks, a crew member is playing a practical joke that was somehow missed in editing. If you look at the left side of Lincoln's face, someone is hitting him with a laser pointer. This is definitely not part of the script (i.e. Sniper rifle scope), as no one is actively targeting members of Fringe in this part of the show. (00:16:20)
Answer: In the time line of Season 4, William Bell is trying to destroy both universes to create a new one, and he needs Olivia to power the collapse. So he helped her escape. But the real question is, if not in search of Peter, why Olivia has to travel to the alternate universe to be captured and replaced?
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