London, 1675: Born to wealth and privilege, Katherine is introduced to the decadent court of King Charles II, and quickly becomes a favorite from the palace to the bawdy playhouses. She gleefully snubs respectable marriage to become the Duke of York's mistress. But Katherine's life of carefree pleasure ends when Charles II dies, and her lover becomes King James II. Suddenly she is cast into a tangle of political intrigue, religious dissent, and ever-shifting alliances, where a wrong step can mean treason, exile, or death at the executioner's block. As the risks rise, Katherine is forced to make the most perilous of choices: to remain loyal to the king, or to England.