Honore de Balzac 
Ferragus [PDF ebook] 

A heartbroken cavalry officer, Auguste de Maulincour, is strolling through a rather seedy section of Paris when he happens to spot the object of his unrequited love, a married young woman named Clemence. Even more remarkable is the fact that he sees her furtively entering a house of ill repute. Aghast and yet intrigued, Auguste begins to follow Clemence — and what he witnesses plunges him into a world of deception and dark secrets.