No one on the remote Welsh island of Broadholm suspects the incredible truth behind the sudden reign of terror that begins after the entire island's livestock go berserk. The ravens that inhabit the island's dark and sinister looking Devil's Tower subsequently embark on a series of horrifically vicious attacks that defy the investigation of Detective Sergeant Rory McNair. At first suspecting black magic, it was not until the unconventional detective discovers that one of the victims was researching both the history of the tower and its guardian ravens that he is able to glean the true nature of the horrendous forces at work.