Fringe is back, and wastes no time in getting right back into the grove of the season. An agent from a separate dimension tries to stop the meeting that occurs between Olivia and who we presume to be William Bell. The attempt on Olivia's life causes her to lose her memories, but not her life, so the agent is once again tasked to kill her. To stop this from happening, Peter and Walter try to learn the identity of the agent, which turns out to be quite difficult because the agent turns out to have a machine which gives him the ability to shape shift. This is on top of the fact that Fringe division is being shut down due to unsatisfactory results, so anything that Peter or Walter want for their investigation is refused. This would have completely halted the attempt to aid Olivia if it were not for Junior FBI agent Amy Jessup who has taken a special interest in Fringe division. With her help, Charlie and Peter are able to corner the assassin. After Charlie supposedly kills the assassin, and Peter takes the shape shifting machine as a bribe to keep Fringe open. But as we see in the final scene of the show, the assassin is still alive, and has taken the appearance of Charlie.
And where is the Observer in this episode? Well thanks to his time off, he turns out to be quite hard to spot, so don't feel to bad if you missed him. If you watch carefully at the very beginning you can see him walking behind the car crash that the assassin was in. There is the picture below with a red box circling him, he is in the center of the picture at the bottom. Here is to another great season!