Teenage Silvie is living in a remote Northumberland camp as an exercise in experimental archaeology. Her father is an abusive man, obsessed with recreating the discomfort, brutality and harshness of Iron Age life. Behind and ahead of Silvie's narrative is the story of a bog girl, a sacrifice, a woman killed by those closest to her, and as the hot summer builds to a terrifying climax, Silvie and the Bog girl are in ever more terrifying proximity.