In this episode, we find England alone - a protestant nation in a largely Catholic Europe. Then, 12 years into Elizabeth's reign, the Pope declares her a heretic, which in the hearts of England's Catholics gives them permission to kill her. Queen Elizabeth looks to her spymaster William Cecil to stop the Catholic assassins getting through. Cecil establishes a huge espionage network - England's first secret service. His spies break Catholic conspiracies at home and abroad.

Robert Cecil is the son of Elizabeth I's original spymaster. He has been groomed since birth to inherit his father's network but when he finally steps into his father's shoes, the Queen's enemies are stronger than ever and Cecil must also watch his back. The Earl of Essex has established a rival network and is trying to oust Cecil as Elizabeth's spymaster.