Sherlock Holmes and Dr. Watson have been tasked by Mary Morstan, the daughter of an officer, to find her father, an Indian colonial officer, who has been missing for ten years. Initially, the search yields no results until Holmes and Watson receive a tip from an unknown source about a certain Thaddeus Sholto, whose father was friends with Mary’s father in India. Both of them are now deceased. What Holmes does not initially know is that upon their return to England, the two had brought back a treasure, which is now in the possession of Thaddeus and his brother. However, the brother is then murdered under mysterious circumstances. The main suspect: Thaddeus Sholto. But Sherlock Holmes has his doubts...