Mary Stuart (Katharine Hepburn), the Queen of Scotland, returns to her native highlands upon the death of her husband, the King of France -- which is one of the rival nations of English queen Elizabeth Tudor (Florence Eldridge). After Mary's third marriage to the Earl of Bothwell (Fredric March), the Scottish people become divided, and Mary is forced to abdicate her throne. She seeks help from Queen Elizabeth, who fears Mary's influence and has her imprisoned, and later executed.