Urquhart, Paul: The Shadow (1908); v1; 14 Oct 2020
 

In the first year or two of the 20th Century, when the Turkish Ottoman Empire is fraying at the edges, and trouble is bubbling in the Balkans, an adventurous young man finds himself drawn into deep trouble when he inadvertently becomes possessor of the "Diocletian Diamond", the near-legendary but still potent symbol of the Kings of the (mythical) Kingdom of Bythnia, wedged in between Russia, German and the Ottoman Empires.

Characteristic helter-skelter adventure yarn of the era, with our hot-headed and impetuous young hero foiling revolutionaries, fighting off Cossack raiders, and even dining with the Kaiser.