Concentrates on Mary's short-lived reign and the battles she has to fight with both her Protestant subjects and the English Queen, Elizabeth 1st (Catherine McCormack).
The story continues with her son James VI of Scotland (who, on Elizabeth's death, became James 1st of England), and the plot against his reign masterminded by the influential Catholic Robert Catesby (Coyle) - a plot planned by Guy Fawkes (played by newcomer Michael Fassbender) to blow up the Houses of Parliament in order to rid the nation of an oppressive Protestant monarch.
