Mary Stuart, who was named Queen of Scotland when she was only six days old, is the last Roman Catholic ruler of Scotland. She is imprisoned at he age of 23 by her cousin Elizabeth Tudor, the English Queen and her arch adversary. Nineteen years later the life of Mary is to be ended on the scaffold and with her execution the last threat to Elizabeth's throne has been removed. The two Queens with their contrasting personalities make a dramatic counterpoint to history.
With the aid of dramatised scenes and location-based interviews with leading historians, this film tells the riveting story of how, over an eight-week period in 1586, England's greatest spymaster used covert espionage techniques to foil a Catholic conspiracy to murder Queen Elizabeth I and engineered the execution of Mary Queen of Scots. Sir Francis Walsingham is recognised as one of history's master spies, thanks to the extraordinary trap that he set for Mary, Queen of Scots. Using a sophisticated network of double agents, informants, and secret codes he allowed Mary to believe that she was master-minding a plot to destroy Elizabeth. In fact, every move Mary made was tracked, by intercepting and decoding her correspondence. As a result, the Scots Queen was exposed as a threat to the Crown, and Walsingham was finally able to persuade Elizabeth to execute her.