Continuity mistake: The front license plate on John's SUV falls off during the chase with Olivia. It reappears seconds later. (01:15:30)
Continuity mistake: On the park bench, while talking to Peter, Olivia's hair moves back and forth over her right shoulder. (00:32:40)
Continuity mistake: At the beginning of the episode, when Christopher is putting Loraine in the car, her stomach changes from bulging outward to flat and normal in one shot.
Continuity mistake: When Olivia says "Freshman", Peter and Walter are seen screw driving wires into Roy's head. In the next shot, the wires are gone and they are drilling in his head. Later on, they use the screwdrivers again. (00:36:30)
Continuity mistake: The bullet hole in Davidson's chest is not at all where he was shot.
Continuity mistake: This episode takes place over one day. It's Olivia's birthday at the start of the episode, and at night, she gets the card from her stepfather, implying that it's still the same day. Right before Broyles yells at Olivia in the Harvard halls, there is an establishing shot of Harvard where it is nighttime outside, but inside the building, there's sunlight coming through the windows.
Continuity mistake: During one of the first shots of Olivia in the tank, you can see the reflections of lab lights on the water even though the tank is closed.
Continuity mistake: Olivia is pretending to be Raoul's friend at the bar where his brother works. When talking to the guy, her hair moves back and forth in front of her right shoulder throughout the whole scene.
Continuity mistake: Near the end of the episode, when Brian Dempsey is threatening to kill himself, the gun he is pointing at Olivia switches hands. He is holding the revolver under his chin with his right hand in closeups, but in shots of Olivia, he is pointing her gun at her with his left hand.
Inner Child - S1-E15
Continuity mistake: Olivia, Broyles, Peter and Walter are visiting the boy for the first time at the hospital. A small bit of Olivia's hair is in front of her left shoulder. Cut to the immediate next shot from the patient's room and all of her hair is behind of shoulder. (00:07:05)
Inner Child - S1-E15
Continuity mistake: This is when Olivia goes to visit the boy at the hospital the second time. She and the guy from Department of Social Services go outside to talk. One of the shots is flipped. Note Olivia's notepad and the heart monitor by his bed. (00:19:40)
Inner Child - S1-E15
Continuity mistake: Olivia stops The Artist at a checkpoint, and he touches his face with his hand. When the shot cuts to Olivia, his hand disappears; when the shot cuts back to The Artist, his hand reappears. (00:43:20)
Inner Child - S1-E15
Continuity mistake: When Olivia calls Broyles to ask him to move the child, the shot of Broyles answering the phone is a recycled shot from the episode "Safe". In addition, the shot is flipped, as can be seen by the fact that Broyles' watch is on his right wrist rather than his left.
Continuity mistake: The blood stain on the door of the Animal Control van changes in size. It's much larger when Olivia runs past it to help Charlie.
Continuity mistake: At the club, when Peter and Olivia are looking for Valeria, Peter is wearing an ear piece in his left ear. When he talks to the woman, the piece is missing.
Continuity mistake: At the very end of the episode when Nina Sharp exits the elevator, she mostly steps out of the elevator completely before the masked men come and shoot her. However, when they review the security footage of the attack in the next episode, "There's More Than One of Everything," you see that she barely takes a step before being shot. (00:49:15)
Continuity mistake: When Olivia crosses over to the other side you see people wearing FBI jackets. But according to later episodes that had changed to Fringe Division on the other side years earlier.
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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