Sherlock Holmes and his brother Mycroft investigate the murder of an amanuensis who clutches a pince-nez and whose last words were, "The professor--it was she."
A nervous landlady brings a mysterious boarder to Holmes' attention, leading to a secret society and the efforts of a young couple to escape their past.
Sherlock Holmes has disappeared into the Highlands, while Mycroft investigates the theft of the Mazarin diamond and Watson suspects a trap in an offer of $5 million to a former professor if he can find a third man surnamed Garrideb.
Susan Cushing asks Holmes' help in solving the disappearance of her sister Mary Browner, but it doesn't seem Holmes' type of case until he is told of a Christmas present's grisly contents.
