Spinster Edith Presbury asks Holmes to investigate when she is frightened by a large hulking figure silhouetted in her bedroom window - a presence which causes her dog to howl. Holmes is convinced the prowler is something out of the ordinary, but Watson at first finds the case trivial.
Colonel James Damery calls on Holmes when the rich and beautiful Miss Violet Merville announces her engagement to Baron Gruner, a dangerous Austrian. Gruner has persuaded Violet that he is not a killer, and Holmes has to establish the truth and foil the powerful baron.
Alice Turner sends for Holmes when her lifelong friend farmer William McCarthy is killed and police suspicion falls on his son, James. James McCarthy admits quarrelling with his father, but he will not explain what their argument was about.
Maria Gibson, the wife of a gold-mining millionaire, is found shot dead at their country house. Gibson asks Holmes to find his wife's killer and thus to clear the name of his children's governess, Miss Dunbar, who has been charged with the crime. Is Gibson acting as a kindly employer, and what are the hidden depths of the case?
Watson, on holiday in the Lake District, meets the enigmatic Lady Frances Carfax, who is being haunted by the ghost of a horseman. Holmes decides to come up to join Watson, but by the time he arrives Lady Frances has vanished without trace. Holmes investigates and becomes very curious about the ghost.