Late December and the river is rising. The Herefordshire village of Ledwardine has not been flooded in living memory; prosperous incomers and weekenders, lured by dreams of woodsmoke and mulled wine, have been assured it will never happen. But in these days of climate change nothing is certain.

Merrily Watkins, parish priest and diocesan exorcist, has learned that one of the incomers, living incognito in a barn conversion, is an author whose aggressive, evangelical atheism has made him a figure of hate for religious fundamentalists. The writer's wife is becoming conspicuously agitated is it the fear of discovery or the kind of fear that she, of all people, could never disclose?

Meanwhile, another kind of religious conflict flares, as the Welsh border county digs up its pagan past. Only days before Christmas, police in the city of Hereford make a gruesome discovery, linked to the unearthing of the a Dinedor Serpent, a unique prehistoric ritual monument threatened by a new road. In Ledwardine itself, a team led by a controversial TV archaeologist is uncovering the buried Bronze Age stones of Coleman's Meadow an exciting time for Merrily's teenage daughter, Jane, but the last thing some people want is for these stones to stand again.

Overnight, the village is isolated in the floods, cut off with a killer inside a new kind of killer for a cold new age. As the waters rise, shocking savagery paralyses an ancient community untangling its own history against the swirling uncertainty of the future.