The Mysteries of Udolpho by Ann Radcliffe is a Gothic romance that presents supernatural phenomenon which is later explained by natural causes. In the novel, Emily St. Albert is orphaned and left to the charge of her aunt whose new husband, Montoni, subjects both Mme. Cheron and Emily to cruelty in order to attain his mercenary ambitions. Confined to Montoni's castle di Udolpho, Emily witnesses many supernatural events. After escaping from Udolpho, Emily returns to France, where eventually all of the mysteries are explained and she is reunited with her love, Valancourt. The Mysteries of Udolpho is a truly engaging and compelling novel.

After Mme. St. Albert dies, M. St. Albert and Emily take a journey for his health. On the journey, they meet Valancourt, who becomes Emily's lover. M. St. Albert approves. M. St. Albert dies, leaving Emily in Mme. Cheron's care. Mme. Cheron encourages Valancourt's courting of Emily until she marries Montoni, who disapproves. Montoni, Mme. Montoni nee Cheron, and Emily move to Venice, where Montoni treats his wife very poorly and tries to force Emily to marry Count Morano. Montoni abruptly departs with his new family to castle di Udolpho in the Apennines. After Count Morano attempts to kidnap Emily because he does not trust Montoni, Montoni dismisses Count Morano and his suit. There are many mysterious events that occur at the castle di Udolpho.

When Mme. Montoni refuses to sign her estates over to her husband's disposal, he imprisons her. Her imprisonment leads to her illness and subsequent death, and Emily inherits the estates which she also refuses to relinquish to Montoni. Emily is imprisoned in castle di Udolpho and learns that there is a French prisoner also contained within the walls who she believes to be Valancourt. With Ludovico's help, she meets the prisoner, Chevalier Du Pont, a long time admirer of Emily. Ludovico helps Emily, Du Pont, and Annette escape to France where they are shipwrecked at Chateau le Blanc, owned by Count De Villefort.

When Emily writes to Valancourt of her return to France, he visits her at the chateau. Unfortunately, Count De Villefort tells Emily of Valancourt's debauchery, and she renounces her lover. Many mysterious events occur at Chateau le Blanc, which makes Emily question her father's relationship with Marchioness de Villeroi, the former mistress of the chateau. Emily spends a lot of time at the nearby monastery of St. Claire. Montoni dies, and Emily claims her aunt's estates. She mourns the loss of Valancourt when she returns to Tholouse and La Vallee. She visits Chateau le Blanc and the monastery of St. Claire where many of the novel's mysteries are solved by the death of Sister Agnes, formerly known as Signora Laurentini. Primarily, Emily learns that the Marchioness de Villeroi was her father's sister. Count De Villefort learns that he is mistaken about Valancourt's character, and Emily and Valancourt are reunited and married.