The Czar's Spy: The Mystery of a Silent Love (version 2) - William Le Queux

A mysterious burgary of the British Consulate at Leghorn, coupled with the even more mysterious visit of an English yacht, leads to a trail of espionage and underground criminal activity that carries to reader to London, to Scotland, and ultimately to Finland, then groaning under the oppression of its imperial Russian masters. Our hero, fortunately, is a man of great perspicacity (half a century later he might have been named Double O Seven), but even he finds his limits tested as he attempts to find the truth. - Summary by Nicholas Clifford