When autumn storms blast Hereford, centuries-old human bones are found amongst the roots of a tree blown down on the city’s Castle Green. But why have they been stolen? At the nearby Cathedral, another storm is building around a new, modernising bishop who believes that if the Church is to survive it must phase out irrelevant archaic practices. Not good news for Merrily Watkins, consultant on the paranormal or, as it used to be known, diocesan exorcist. Especially as she’s now presented with the job at its most medieval.

In the moody countryside on the edge of Wales, a rambling 12th-century house is thought to be haunted. Although its new owners don’t believe in ghosts, they do believe in spiritual darkness and the need for exorcism. But their approach to Merrily is oblique and guarded. No-one can be told - least of all, the new bishop. Merrily’s discovery of the house’s links with the medieval legend of a man who resisted mortality threatens to expose the hidden history of a more modern cult and its trail of insidious abuse. A trail that may not be closed.