The Fringe Team investigates a pocket reality occupying an apartment building, and Peter learns that he has the power to stop the Observers.
One of the things that I've 'observed' since this season began is that with each successive episode, the story has grown darker. Walter's brain getting scrambled (again!) Desmond losing his head (literally!) and the heartbreak of getting us to really like and care about Etta and then killing her.
This show is rockin' so far, and I think the ante will be up even higher now that Peter has stuck that thing in his neck and become 'one with the Borg', as it were.
If I did the math right, I think after next week's ep, we'll have a four week hiatus, then then four weeks leading up to the finale, which will be the final two eps. Should be a heck of a ride.