Following the death of her father, Emily St. Aubert finds herself imprisoned within the foreboding walls of Udolpho, where she must navigate the machinations of her sinister guardian and the unsettling secrets of the castle. Emily seeks to maintain her autonomy and remain faithful to her beloved Valancourt while facing the predatory intentions of Signor Montoni. The narrative framework utilizes a third-person perspective to detail the physical isolation of the Italian Apennines and the psychological pressure exerted by the castle's claustrophobic environment. Emily must rely on her reason and moral fortitude to distinguish between genuine supernatural threats and the calculated deceptions of those around her.

Readers frequently highlight the atmospheric density of the prose, which emphasizes the sublime power of nature and the architecture of the castle. Discussion often centers on the author's ability to build suspense through the protagonist's internal reactions to her environment. Critics note that the pacing is deliberate, favoring long, descriptive passages over rapid action sequences. The work is recognized for establishing many conventions of the Gothic genre that influenced later writers. Readers often appreciate the balance between the heroine's emotional vulnerability and her eventual triumph over external threats.