It's 1825, four generations after Berggrund Island's women stood accused of witchcraft under the eye of their priest, now long dead. In his place is Pastor Silas, a widower with two wild young daughters, Beata and Ulrika. The sisters are outcasts: imaginative, oppositional, increasingly obsessed with the lore and legend of the island's dark past and their absent mother, whom their father refuses to speak of.

As the girls come of age, and the strictures of the community shift but never wane, their rebellions twist and sharpen. Ever capable Ulrika shoulders the burden of keeping house, while Bea, alone with unsettling visions and impulses, hungers for companionship and attention. When an enigmatic outsider arrives at their door, his presence threatens their family bond and unearths - piece by piece - a buried history to shocking ends. All the while Berggrund's neighboring island The Blue Maiden beckons, storied home of the Witches' Sabbath and Satan's realm, its misted shore veiling truths the sisters have spent their lives searching for.