Late December and the river is rising. The Herefordshire village of Ledwardine has not been flooded in living memory but in these days of climate change nothing is certain. Merrily Watkins, parish priest and diocesan exorcist, has learned that one of the incomers is an author who is a figure of hate for religious fundamentalists. Meanwhile, the Hereford police make a gruesome discovery linked to the Dinedor Serpent, a unique prehistoric monument. In Ledwardine itself, buried Bronze Age stones have been unearthed. Overnight, the village is isolated in the floods, cut off with a killer inside. As the waters rise, shocking savagery paralyses an ancient community untangling its own history against the swirling uncertainty of the future.