Dr Michael Cullen is the American historian on holiday in Ireland with his wife, Karla, and their two children. They rent the large and secluded Blacklands House for its tranquillity and convenience for Cullen to complete his research on Irish folklore. Troubled by persistent dreams of a strange woman dressed in white who combs her hair and screams, Cullen blacks out completely when he seems to meet her for real in the broad light of day. Retrieving only an ancient comb carved from bone, he puts the experience down to an hallucination of his fatigued imagination. But Maeve Quill, the expert on Celtic myth and language who is Cullen's research assistant, suspects too late that he and his family are being haunted by the supernatural creature whose unearthly cry is the harbinger of death. For when Karla is apparently frozen stiff on a hot summer night, she is merely the first casualty in the horrifying spiral of death and destruction that follows.