Dr. Watson (Robert Duvall) becomes convinced that his friend Sherlock Holmes (Nicol Williamson) is delusional—particularly in his belief that Professor James Moriarty (Laurence Olivier) is a criminal mastermind—as a result of his cocaine addiction. Moriarty visits Watson to complain about being harassed by Holmes. Watson enlists the aid of Sherlock's brother, Mycroft Holmes (Charles Gray (actor)), to trick Holmes into traveling to Vienna, where he will be treated by Sigmund Freud (Alan Arkin).