Why is the observer dropping in on Olivia? Since it is this observer in particular, September (played by  Michael Cerveris), it could be anything from making a move towards fulfilling his order to fully erase Peter, to the exact opposite - beginning the process of settling all of this Universe slap-chop once and for all.  Certainly when any lead character sits down for a discussion with the Observers major things are set to happen.  This could signal a turning point for Fringe's fourth season.  The talk out of the Fringe writer's room has been that the multiple Universe thing will be resolved, so now is as good a time as any to get things going.

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