Olalla by Robert Louis Stevenson

"Olalla" was a "shilling shocker" written for the Christmas season in 1885, just before the publication of Stevenson's Dr. Jekyll and Mr. Hyde. The nameless protagonist of this Gothic tale, a wounded soldier, goes to the Spanish countryside to recuperate. He finds himself enthralled by the beautiful Olalla, the daughter of his hostess, whose family conceals a terrible secret.