'Anyone who's prepared to kill for a book interests me.'

Ireland, 1006. Strange things have been happening at the isolated Abbey of Kells: disembodied voices, unexplained disappearances, sudden death. The monks whisper of imps and demons. Could the Lord of the Dead himself be stalking these hallowed cloisters?

The Doctor and his companion find themselves in the midst of a medieval mystery. At its heart is a book: perhaps the most important book in the world. The Great Gospel of Columkille. The Liber Columbae.