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...

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.