Sherlock Holmes and the Hentzau Affair

In this mashup of genres Sherlock and Dr. Watson meet "The Prisoner of Zenda".

Colonel Sapt of the Ruritanian Court journeys to England on a secret mission to save the country from anarchy. His mission is to engage the services of Rudolf Rassendyll once more to impersonate the King while the monarch recovers from a serious illness. But Rassendyll has mysteriously disappeared. In desperation, Sapt consults Sherlock Holmes who, with his faithful companion Watson, travels to the Kingdom of Ruritania in an effort to thwart the plans of the scheming Rupert of Hentzau in his bid for the throne.

"Sherlock Holmes and the Hentzau Affair" is a wonderful blend of detective story and rousing adventure yarn.