Elizabeth remains a threat in her childless Catholic sister's eyes. Queen Mary is still on the throne and with her harsh politics, she excessively pursues the persecution of Protestants, even of her sister. Queen Mary knows that her sister has a large number of supporters in England, and therefore, she imprisons Elizabeth in the tower and later puts her under house arrest. When Queen Mary surprisingly dies from a tumor, Elizabeth becomes Queen of England. William Cecil, her advisor, warns Elizabeth of the dangers that the married Robert Dudley may, due to their inappropriate relation, cause as a member of the Privy Council. (thetvdb.com)