The half-sisters Elizabeth and Mary

At the age of 21, a young woman called Elizabeth found herself imprisoned in the Tower of London. She had been accused of plotting to take the throne by her older half-sister Mary, who was queen. It was very likely that Mary might order her to be executed, so Elizabeth wrote her a letter saying she was innocent. Although Mary refused to see Elizabeth, she eventually freed her and Elizabeth's life was spared. Soon after, Mary died and Elizabeth became Queen of England.