When Sara and Fergus move to the wild coast of Scotland after the death of their son, a gruesome discovery unleashes an evil spirit that has lain dormant for centuries. Sara becomes possessed and Fergus is overwhelmed by the challenge of saving his wife. He summons the local priest to perform an exorcism which goes horribly and fatally wrong. Fergus then turns to Mungo, a mysterious local man to help him battle the violent spirit that has possessed his wife.