Either the visual effects people did a great job, or there is a damn hideous creature out there, because that worm creature was freaky, slimy, and hard to watch. The scene showing all the dead bodies with worms literally made my stomach turn. That set the tone for the episode which was solely a standalone. The writers finally decided to have a standalone episode that had no apparent relation to the Pattern which was nice. It was just science gone way wrong.
Olivia again did not have much to do, and Peter took the reigns doing much of the work, almost getting killed in the end. This season, and especially the past few episodes, Peter has shown the drive and initiative that his character had been lacking. I felt Joshua Jackson had been wasted making one-liners in the background, but with the showcasing of his abilities, I think his character is going in the right place.
John Noble did a brilliant job which shouldn't come as a surprise anymore. The writers know exactly how to deal with Walter, and John Noble executes their ideas perfectly. He is a broken man, who while out of the mental hospital, still harbors the same psychotic tendencies he had. It's not like he has had time to re-acclimate into the world. He is thrown into the work of the FBI, work that pushed him to be institutionalized in the first place. He may not be able to survive on his own, but there is part of him that wants to be independent, to be free from the burdens he has, but he cannot run from them. There is a barrier that he tries to climb over -- this week going out on his own -- but in the end he comes back down unable to go forward.