1372, Widow Lady Katherine de Swynford presents herself for a role in the household of royal prince, John Plantagenet, Duke of Lancaster, hoping to end her destitution. But the Duke's scandalous proposition leaves her life of pious integrity reeling. Seduced by the glare of royal adoration, Katherine becomes John's mistress. She will leave behind everything she has stood for to play second fiddle to his young wife and ruthless ambition. She will live in the shadows of the most powerful man in England in the hope of a love greater than propriety.