Neville St Clair works in the City of London and is a man of very regular and respectable habits. One day, his wife goes into town for lunch and is shocked to see her husband in the window of an opium den. That evening, he fails to return home, and Mrs St Clair decides to consult Holmes.

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...