At the castle of Udolpho in the Apennines where Emily, the heroine of Mrs. Radcliffe's classic 'thriller', has been taken by Signor Montoni, the Italian villain, mystifying things happen. There are hints of murder and robbery, apparitions, and carefully guarded secrets, all of which in the end are ingeniously explained. Usually classed as a "horror novel', The Mysteries of Udolpho should rather be described as a 'terror novel', for Mrs. Radcliffe avoided the gruesome and the repugnant while providing all the tension of fear and of expectation. The good and the bad characters are sharply distinguished, as it was the author's belief that, 'though the vicious can sometimes pour affliction upon the good, their power is transient and their punishment certain'. Udolpho is very much a romance of its time; its perennial popularity is explained by the literary skill and shrewd common sense Mrs. Radcliffe brought to the conventions of that form. The text of the present edition by Bonamy Dobrée is based on the first edition of 1794. First published in 1966 in the Oxford English Novels series, the edition is now augmented with explanatory notes by Frederick Garber, Professor of English at the State University of New York at Binghamton.