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 Sign of Four (1983 film) Hound of the Baskervilles" were ultimately filmed as Granada Television's "Sherlock Holmes" series premiered in 1984. In an interview with "Scarlet Street", Ian Richardson explained: "The Sign of Four" was shot simultaneously with "The Hound of the Baskervilles" but the schedule precluded having David Healy portray Watson in both films so Donald Churchill was enlisted to play the role in "The Hound of the Baskervilles". Two previous Watsons appear in the film: Terence Rigby who played Watson to Tom Baker's Holmes in 1982s "The Hound of the Baskervilles" and Thorley Walters who played Watson three times previously; with Christopher Lee