Invited to the court of the charismatic King Charles II, the high-spirited young Robert Merivel cheerfully abandons his medical studies to accept the post of Royal Physician. At the King's request, he enters into a marriage of convenience with Celia, the youngest Royal mistress. In return for knighthood and a country estate, the King commands Merivel to forgo any conjugal rights to his bride. But Merivel is unable to control his lust for Celia. She firmly rebuffs his advances, and the King, enraged at Merivel's disobedience, strips him of his land and title. He is forced to seek shelter within the confines of an austere Quaker hospice run by a former medical colleague. Once again, Merivel falls prey to the temptations of the flesh, and seeks solace in the arms of Katherine, a patient. Found out and expelled, Merivel takes the now pregnant Katherine back to London. At last he harnesses his resources and in the face of extraordinary adversity, redeems himself as a physician and a man.