This 5th Season features adaptations of short stories found in Doyle's book, "The Case-Book of Sherlock Holmes".
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.
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?
Sir Robert Norberton stakes a huge amount (much of it borrrowed) on his horse Shoscombe Prince winning a race. His trainer thinks Sir Robert has gone mad and consults Holmes. Then one of the many creditors disappears and human bone is found in a furnace...
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.
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.
The daughter of scientist Professor Presbury sees her father's face at her second-storey window; Holmes connects this with recent zoo thefts.