(Note: SPOILER WARNING!)
The biggest part of the episode was Walter and his brain. Literally, his brain. Like the 3 pieces of the hippocampus that were removed. I had just one qualm about that whole bit. When Olivia and Peter are looking at the X-rays and Olivia asks something along the lines of "What's the hippocampus for?" ... Olivia, I'm sure that you went through high school and college and at least took an anatomy and/or psychology course and learned what the hippocampus does. ANYWAY ... my FAVORITE Walter moment in the entire episode was when Newton temporarily restored Walter's memories to his brain. For a short while, Walter was ... whole again. It was very satisfying to see him with all his marbles. How sad that it can't happen again.
But back to the title of this posting! We, the viewers, were presented with 1) the leader of the opposition who is in our world (Thomas Jerome Newton), 2) what he looks like, and 3) his overall goal. However, with Olivia's decision to save Walter, he escaped. As for his future plans, we don't know. But the ending tag of the episode really brought things full circle in a way: we now know why Walter isn't all there. It was a decision between Walter and William to protect the doorway to the parallel universe, but at what cost you ask? Oh, Walter will be not quite there. For the rest of his life. Yeah. It sucks. Royally.
Wait! Kind went off on a tangent there! Okay. While the end of the episode was as big a cliffhanger as the fall finale from last season (David Robert Jones's mysterious escape from a German prison) or the season finale from last season (in which Olivia met with William Bell in the still existing World Trade Center in a parallel universe), it was still ... unnerving, perhaps? We know Newton's motive, but we don't know his next moves. It's almost like a chess game. We took some pieces from the opposing player, yet we have a feeling that he has an ace up his sleeve and he's plotting our downfall somehow. We don't know when it'll happen, but we know that it'll happen.
So, what's to come in the second half of Fringe's second season? We don't know. But we're waiting with baited breath.