Audio problem: When Olivia calls Astrid to tell her it wasn't Walter's research, we cut to Astrid who says, "Good news", but her lips do not move. (00:33:57)
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.
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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