In the early 18th century, with England at war with France, a frail Queen Anne occupies the throne, alongside her close friend, Lady Sarah Churchill, Duchess of Marlborough, who effectively governs the country in her stead due to Anne’s ill health and mercurial temper. However, when Abigail, a distant relation of Sarah's arrives as a new servant, she sees an opportunity to advance her position and a power struggles between the two women ensues to become the queen's favorite, which threatens an entire nation.