After a shaky start to the season last week, Fringe gets back on track with a fascinating episode highlighting the major plot points and problems going ahead. I had my doubts, but I'm on board and expecting a great final season (baring any ratings miracles).
"One Night in October" ties everything together with the case of the week--Olivia bringing a professor to the other world in order to profile his counterpart, a serial killer. This interesting reversal hinges on the fact that the professor had a woman in his life, Marjorie, who helped him while the killer did not. Bringing the two worlds together, we see some engrossing interactions with the doubles--both between the professor and the serial killer, and the two Olivias who seem to be warming to each other (or at least they understand each other better).
Paralleling the extraction of the memory of Marjorie, Peter has been erased from everyone's minds. But as Broyles suggest, though the memory may be erased, they may also leave an indelible mark on the person. Indeed, this looks to be true, as every character indicates they have something missing. Walter, however, tries to ignore this by drowning himself in music, blocking out Peter's cries.