Norfolk, 990 AD. Deep in the Fens, isolated by a vast and treacherous mere, an order of holy sisters make their home. Under the steely guidance of Abbess Sigeburg they follow God's path, looking to their infirmarian, Hilda, to provide what comfort and cures she can. But when the mere takes a young servant boy, Sigeburg's grip falters and Hilda quickly realizes this place holds secrets darker and more unholy than she can fathom. Then proud Sister Wulfrun, a recent arrival to the convent, has a vision: a curse is upon them, and change must be brought. Is she saint or serpent? To Hilda, Wulfrun is a signal bolder and brighter than any fire set - one she cannot help but follow . . .