Sir Francis Walsinghamâ€™s official title was principal secretary to Queen Elizabeth I, but in fact this pious, tight-lipped Puritan was Englandâ€™s first spymaster. A ruthless, fiercely loyal civil servant, Walsingham worked brilliantly behind the scenes to foil Elizabethâ€™s rival Mary Queen of Scots and outwit Catholic Spain and France, which had arrayed their forces behind her. Though he cut an incongruous figure in Elizabethâ€™s worldly court, Walsingham managed to win the trust of key players like William Cecil and the Earl of Leceister before launching his own secret campaign against the queenâ€™s enemies. Covert operations were Walsinghamâ€™s genius; he pioneered techniques for exploiting double agents, spreading disinformation, and deciphering codes with the latest code-breaking science that remain staples of international espionage. In the taut narrative of a spy novel, Budiansky recounts how this legendary spymaster invented the art and science of modern espionageâ€”and in the process set Elizabethan England on the path to empire.