This absorbing account of Catholic and anti-Catholic plots and machinations at the English, French, and exiled Scottish courts in the latter part of the sixteenth century is a sequel to John Bossy's highly acclaimed Giordano Bruno and the Embassy Affair. It tells the story of an espionage operation in Elizabethan London that was designed to find out what side France would take in the hostilities between Protestant England and the Catholic powers of Europe. France was a Catholic country whose king was nonetheless hostile to Spanish and papal aggression, Bossy explains, but the king's sister-in-law, Mary Queen of Scots, in custody in England since 1568, was a magnet for Catholic activists, and the French ambassador in London, Michel de Castelnau, was of uncertain leanings. Bossy relates how Queen Elizabeth's Secretary of State, Sir Francis Walsingham, found a mole in Castelnau's household establishment, who passed information to someone in Walsingham's employ. Bossy discovers the identity of these persons, what items of intelligence were passed over, and what the English government decided to do with the information. He describes how individuals were arrested or fled, a political crisis occurred, an ambassador was expelled, deals were made. He concludes with a discussion of the authenticity of Elizabethan secret operations, arguing that they were not theatrical devices to prop up an unpopular regime but were a response to genuine threats of counter-revolution inspired by Catholic zeal.