Client and later wife of John Watson. First appears in The Sign of the Four as the woman who brings the case of the Agra treasure to Holmes and Watson.
Background
- Father: Captain Arthur Morstan, 34th Bombay Infantry; disappeared in London in 1878 (before the novel begins)
- Occupation at time of Sign of Four: governess (Mrs. Cecil Forrester’s household)
- Receives annual anonymous pearls — the mystery that brings her to Baker Street
Role in The Sign of the Four
Mary’s father’s disappearance is connected to the Agra treasure: he and Thaddeus Sholto’s father both knew about it. She is both client and love interest — Watson’s attraction to her grows throughout the novel, and Holmes observes it with detached amusement.
The resolution of the treasure — it is lost at the bottom of the Thames when Jonathan Small throws it overboard — removes the wealth that would have made Watson feel unworthy of her. He proposes immediately after; she accepts.
Later references
Mary is referred to as Watson’s wife in subsequent stories but largely remains offstage. Her death is mentioned in passing in The Adventure of the Empty House (EMPT). Doyle was never especially interested in Watson’s domestic life and treats it somewhat carelessly.