The sudden death of Emily St. Aubert’s father leaves her orphaned and under the control of her aunt’s sinister husband, Signor Montoni, who imprisons her within the foreboding walls of the Castle of Udolpho. Emily must navigate a landscape of psychological terror and physical confinement while attempting to maintain her virtue and independence against the machinations of her captor. The narrative framework utilizes a third-person perspective that emphasizes the protagonist's internal emotional state and her reactions to the sublime, often threatening, natural environments of France and Italy. As she encounters unexplained phenomena and potential supernatural threats, Emily relies on her reason and moral fortitude to survive the escalating dangers posed by Montoni and his associates.

Discussion often centers on Radcliffe’s mastery of atmospheric tension and her ability to evoke the sublime through descriptive prose. Readers frequently highlight the deliberate pacing of the novel, which prioritizes internal reflection and environmental detail over rapid plot progression. Critics often examine the work as a foundational text of the Gothic genre, noting its influence on later writers who utilized similar motifs of damsels in distress and haunted settings. The balance between the protagonist's emotional vulnerability and her eventual triumph remains a primary point of interest for those studying the evolution of the novel. Many readers appreciate the way the author manages to sustain suspense through the careful withholding of information regarding the mysterious events at Udolpho.