Alan Bates narrates this documentary series that examines the covert world of espionage and looks at some the most famous spies in history, including Mata Hari, Nathan Hale, Donald Maclean, Anthony Blunt, Violette Szabo and others. The segment "Tools of the Trade" reveals some of the devices and common objects used by spies, while "Cloak & Dagger" looks at assassins and saboteurs, and "To Catch a Spy" explores counterespionage and double agents.