In Aug 1971, Carol Quinlan, a young Canadian student studying in Belfast, Northern Ireland, visits the north-Antrim town of Ballycastle and is intrigued by the story of the Black Nun, the legendary ghost reputed to haunt the nearby ruin of Bonamargy Friary. In a quest to learn more, Carol visits the friary and has a horrifying experience which leaves her beset by recurring nightmares. The frequency of these nightmares lessens during the years that follow only to intensify again towards the turn of the century, until Carol, sleep-deprived and distraught, is compelled to return to Bonamargy to finish the quest started over thirty years before and hopefully bring her nightmares to an end.