The mysterious death of Sir Charles Baskerville is blamed on a longstanding curse that has followed his family for 200 years, a supernatural hound who roams the moors. Detective Sherlock Holmes attempts to uncover the truth.
Mary Morstan, a young governess, has been receiving a rare and lustrous pearl annually from an anonymous benefactor. This mysterious person now wants a meeting. Anxious and bewildered, Miss Morstan enlists Sherlock Holmes and Dr. Watson to escort her to this meeting.
Legendary opera star Irene Adler is threatening to destroy the King of Bohemia's reputation with proof of their illicit affair. The evidence? A photograph. Her ransom? The king's hand in marriage.
Sherlock Holmes and Dr. Watson are called to Whitechapel after learning about a series of strange murders only two years after the Jack the Ripper murders in the same neighborhood.<ref name="bsd"/> The local belief is that the killings are the work of a vampire brought back from a recent mission in Guyana. As they investigate the deaths, they engage in an ongoing debate about the supernatural, with Watson believing in the possibility of vampires and Holmes remaining skeptical until he is able to prove the murders are the works of a living human, rather than any undead creature. At one point, the investigation leads them to the psychic Madame Karasky, who says that Holmes will be saved by the church. Shortly thereafter, Holmes is pushed in front of a moving carriage by the supposed vampire, only to be saved by a pedestrian. In order to catch the murderer, Holmes disguises himself as a monk and reveals that the vampire was Brother Abel, who hoped to get revenge on the monks who didn't listen to him when he believed that the bats were causing rabies in the South American mission, when he was infected. The film ends at Baker Street, when Mrs. Hudson gives Holmes his pipe, delivered by the same man that saved Holmes from being run over. When Holmes asks his name, Mrs. Hudson says his name was Reginald Church.