Mary Tudor (Glynis Johns), sister of King Henry VIII (James Robertson Justice), vainly loves Charles Brandon (Richard Todd), a man of much virtue but no social title. Charles, heartbroken, leaves London, but when Mary runs after him, he's locked in the Tower of London, and freed only when she marries King Louis XII of France. With the meddling Duke of Buckingham also competing for Mary's hand, the lovers must overcome considerable obstacles to live happily ever after.