Dawnlands by Philippa Gregory

It is 1685 and England is on the brink of a renewed civil war against the Stuart kings with many families bitterly divided. Alinor, now a successful businesswoman, has been coaxed by the manipulative Livia to save Queen Mary from the coming siege. The rewards are life-changing: the family could return to their beloved Tidelands, and Alinor could rule where she was once lower than a servant.

Inspired by news of a rebellion against the Stuart kings, Ned Ferryman returns from America with his Pokanoket servant to join the uprising against roman catholic King James. As Ned swears loyalty to the charismatic Duke of Monmouth, he discovers a new and unexpected love

Meanwhile, Queen Mary summons her friend Livia to a terrified court. Her survival, and that of the Stuart kings, is in the balance, and only a clever and dangerous gamble can save them…