Three women controlled by one man – their charismatic husband Elijah, leader of their cult who dictates every aspect of life in the remote Scottish settlement of Halcyon. But cracks have begun to form in the community's idyllic facade, and Elijah's increasingly erratic behaviour begins to test the loyalty of the women who love him, especially when he reveals his intention to take a fourth wife, sixteen-year-old Mim. Deceived and isolated by the husband they share, Aoife, Ruth, and Deborah must set years of animosity aside and come together as danger mounts within their isolated community.