Mary Villiers, Duchess of Richmond and Lennox, is a ravishing beauty raised as the adopted daughter of Charles I of England. In 1642 she is shocked to find herself opposed to her king when he decides to declare war on Parliament and therefore on his own people. Mary embarks on a dangerous quest to help save the throne of England for its rightful monarch, but first she'll tangle with the king's charismatic nephew, Prince Rupert of the Rhine.