While I was watching the episode, I kept thinking of an episode of the cartoon Johnny Test in which moles were pulling objects and people underground. The episode is still ingrained in my brain, and the whole time I was expecting to see an entire mole civilization thriving underground. Alas that never happened but nonetheless the story was intriguing.
It was a typical standalone episode prompted by the disappearance of people. What started as a possible connection to Olivia's disappearance became a search for missing guy who was pulled underground. Apparently you can make mole people by genetically modifying them while still gestating. There was that much time dedicated to the mole man story though I found it pretty cool. It was an above average monster of the week which was fine.
I liked how the writers still tried to add a lot of the main storyline into this standalone though I think it could be problematic, which I'll elaborate on later. Walter explains his alternate universe theory again and says that people who have traveled between them are changed. Olivia has superhearing and supervision now which help in the case though she almost kills Peter in arguably the most shocking moment of the episode. Nina Sharp approaches Olivia and tells her where to find some specialist. At the end of the episode, Olivia meets him.
Broyles and Peter's huge plan to fight back is apparently doing well as the most trouble they're having is getting a C-130. Agent Jessup was thankfully scare in the episode and found some evidence hidden in a Bible which goes along with her persona. Charlie clone was up to no good again with his (it's?) awesome typewriter.
The problem with the half the episode being monster of the week and half serialized is that the middle just doesn't produce very good of anything. Spending time on the monster story takes away from the main Pattern story and vice versa. Networks often like standalone episodes because anyone can jump in and start watching, but adding serial elements like the Charlie replacement would surely confuse the average viewer. Fans of the show are extremely intrigued by the alternate universe stuff after the season one finale and are waiting to see what will happen with that.