After a massive two-part mythology epic that threatened to tear the fandom apart, it's good to see a more typical episode come down the pipeline. Oddly enough, the advance comments from the mainstream press were largely negative. Entertainment Weekly, for instance, bemoaned how boring these "monster of the week" installments were becoming.
It doesn't seem to matter that these stories have been part of the show's DNA since the pilot. I'm not sure this particular episode adheres to any specific urban legend, but most of the first season was about the Brothers Winchester hunting down the truth behind the grisly and horrifying myth. It's funny how the mainstream critics, the ones who ignored the show in its early glories, are now seemingly invested in each and every writing choice, now that it's regaining its ratings momentum.
What those critics have missed, time and again, is the purpose of these supposedly stand-alone episodes. The story is never really about the monster or the legend; it's about the Brothers Winchester and their psychological issues. In particular, this one is all about Dean. Now that we know the truth about his time in Hell, his actions and decisions since the season premiere make a lot more sense. And Dean's emotional and psychological scars can be explored, which is always a nice touch.
Dean is seriously messed up. There's just no other way to put it. He's put on the brave and stoic face regarding his time in Hell for a good long time, but that mask is starting to crack and shatter and it's all he can do to hold it together. Hunting evil and saving people did the trick for a while, but it's just not enough anymore. And poor Sam is at a loss, because what could he possibly do for his brother at this point?
Worse, Dean's issues are leading to mistakes. It was not smart to split up the family. Never mind the sexist decision to toss the women in the shed and let the men hunt the monster. That creepy little flower in the attic was running around and getting into places they couldn't predict. It stands to reason that she could find a way into the supposedly impregnable shed. The smart move would have been keeping the entire family in the shed to play prevent defense, letting the experienced hunters take the offense. But Dean wasn't thinking clearly at all, between intense guilt, self-loathing, and lack of sleep, and Sam hasn't gotten to the point where he's willing to take the reins.
As usual, those character dynamics made the episode work. The family's personal troubles seemed extraneous for the longest time, until the parallels emerged. The father kept insisting that everything would be all right, that it would all work out, no matter how the circumstances changed, but clearly it was self-delusion. Meanwhile, Dean was doing exactly the same thing. It was not the most subtle writing in the show's history, but it worked.
If there was a weakness in the episode, it was the monster itself (or themselves, to be accurate). How exactly would they have managed to learn how to read, write, or speak is a complete mystery. And why would the diary only refer to the daughter, if there was also a son of roughly the same age? By the end, it doesn't quite add up. Thankfully, the monster was just another means to an end, and the core of the episode was more than strong enough to take up the slack.