Count Zarka

Herr Galabin has been instructed by Gersdorff, the Minister, to find and bring back the missing prince Roel. Even thou the Minister hesitates to propose such a delicate and dangerous undertaking to Galabin, the Minister leaned back in his chair thoughtfully stroking his mouth with his long white fingers. "The mystery surrounding the extraordinary disappearance of Prince Roel of Rapsberg deepens every day. I say deepens, because, as you know, the agents of our Bureau, all the machinery which we have set working to elucidate it, have given us absolutely blank results. Had it been a mere piece of eccentricity of the Prince's part, the result, as has been hinted, of disappointment in a love affair, we must have found him, or at least some clue to the direction in which he had disappeared. A man, let alone a prince, cannot vanish from the face of the earth without leaving some trace."

Even thou the book was published in 1903, it's a cleverly written romance and suspense with loads of intrigue, which even fascinates in modern times.