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 Stapleton was, in fact, Rodger Baskerville's son, also named Rodger. His now-widow is a South American woman, the former Beryl Garcia. He supported himself through crime for many years, before learning that he could inherit a fortune by murdering his uncle and cousin. Stapleton had taken Sir Henry's old boot because the new, unworn boot lacked his scent. The hound had pursued Selden to his death because of the scent on Sir Henry's old clothes. Mrs Stapleton had disavowed her husband's plot, so he had imprisoned her to prevent her from interfering. The story ends with Holmes and Watson leaving