Katherine comes to the court of Edward III at the age of fifteen. The naïve convent-educated orphan of a penniless knight is dazzled by the jousts and the entertainments of court. Nevertheless, Katherine is beautiful, and she turns the head of the King's favourite son John of Gaunt. But he is married, and she is soon to be betrothed. A few years later their paths cross again and this time their passion for each other cannot be denied or suppressed. Katherine becomes the prince's mistress, and discovers an extraordinary world of power, pleasure and passion.