The Mysteries of Udolpho (Ann Radcliffe, 1794)

An intricate story with a great many subplots that all eventually tie into one another, but in outline, a young woman becomes the ward of a evil man after her father’s death who keeps her imprisoned in a possibly haunted castle in a effort to steal the estates she inherited from her aunt, who was also briefly her guardian and was also evil, but not as evil. What shocking thing did she see behind the black veil? You won’t find out until the very, very end. What terrible phrase did she glance at before burning the papers? You never really know.