The Hounds of Baskerville order to test his theory. He also points out Sherlock was wrong for once; he believed the drug was in Henry's sugar and put it in John's coffee. In the closing scenes, Mycroft oversees the release of Jim Moriarty (Andrew Scott) from a holding cell in which he has written Sherlock's name all over the walls. The story is based on Arthur Conan Doyle's novel "The Hound of the Baskervilles", and also contains plot devices and lines from other Doyle stories: In June 2011, it was announced that Russell Tovey would appear in "Sherlock" series two in its second episode.
The Hound of the Baskervilles Sir Henry is walking home across the moor. Shooting the animal dead in the struggle, Sherlock reveals that it was a perfectly mortal dog - a mix of bloodhound and mastiff, painted with phosphorus to give it a hellish appearance. They find Miss Stapleton bound and gagged inside the house, while Stapleton apparently dies in an attempt to reach his hideout in a nearby mine located at the heart of the Grimpen Mire. They also find Sir Henry's boot, which was used to give the hound Sir Henry's scent. Weeks later, Holmes provides Watson with additional details about the case.