Review: Sherlock "The Hounds of Baskerville"

In a nod to a lesser known, lesser adapted Holmes story "Black Peter," the episode opens with Sherlock arriving back at the flat covered in blood and carrying a harpoon he used to spear a pig that morning. He had to take the tube home "None of the cabs would have me." With that slightly gorey start, writer Mark Gatiss takes us on a horrific adventure into Dartmoor on the tail of a giant hound. Henry Knight arrives on the morning train asking for Sherlock and John to help him. Twenty years before, his father was ripped apart in front of him by what seemed to be demon hound- possibly an escaped genetic experiment from Baskerville, a government testing facility nearby.
The episode did a great job of inverting some of the expectations that Holmes fans would have for an adaptation of Hound of the Baskervilles. No longer set in a creepy country home haunted by a curse, it takes the story to that modern haunted house, a laboratory where anything could lurk. Many moments of pure psychological terror were in store for all of the characters, even Sherlock our cool logictician. How can Holmes deal with fear and doubt, the inability to trust his own senses? How can Watson deal with such a Holmes?
Our two leads had an opportunity to explore a new aspect of their relationship. One where Sherlock tests certain limits. More importantly, we see John hurt by Sherlock when he insists in one taut scene, "I don't have friends!" By the end though, Sherlock has to relent that he doesn't have friends, just one friend.
Though the episode pays homage to Doyle's original creation, it steps boldly into new territory, allowing itself to differ from the original. Hound is the most adapted Sherlock Holmes story, one that carries with it a lot of baggage. Gatiss sheds much of that baggage by reinventing several aspects of the story and giving fans something fresh and original, something they won't be as familiar with.
Overall, it was a very strong episode. It continues on the momentum created by the raucous first episode and keeps giving us something new from our characters, which can be hard when they are so established in the public consciousness.

*Here there be spoilers:*
One small issue I did have with episode was how the characters were exposed to the hallucinogen. It wasn't in the sugar as Sherlock originally assumed, so how did it get into John's system? Before he goes into the lab, there is a pipe spurting steam and we see the passage fill with it a bit, but would a top government lab allow drugs to freely flow in its laboratories? Unless we assume that Franklin was slipping what was usually a small amount of the drug to his colleagues. That does seem like a plot hole that could use some patching.
The ending was an interesting gear up to next week's episode. Mycroft has clearly made good on his vow at the end of "Scandal" to give Moriarty some of his attention, but since he doesn't get his hands dirty, is forced to let him go. The eerie graffiti all over the holding room shows us that Moriarty has reached a new level of obsession. This version of Moriarty has been a little hard for some to swallow, but I think it's interesting. Why do the same old thing over again?
This Moriarty is a little younger, a little more childlike (which makes him a good counterpoint to our younger, sometimes immature Sherlock). He is clearly intelligent, running a huge criminal enterprise, but Sherlock has become his one obsession. Maybe it's the crack in his lens, maybe his obsession will make him vulnerable? We'll see this Sunday.