The Spy of the Rebellion follows the activities of Allan Pinkerton, famous American detective and spy, during events leading up to and during the American Civil War. By his own admission, in 1861 Pinkerton led a group of agents who foiled a plot to assassinate President-elect Abraham Lincoln. Later, under the pseudonym of Major E. J. Allen, Pinkerton was in charge of an organization which carried out an intelligence and espionage for General George B. McClellan. The book is filled with the amusing stories about spy work and methods used by Pinkerton to recruit and manage agents.

Allan Pinkerton (1819-1884) was a Scottish American detective and spy, best known for creating the Pinkerton National Detective Agency. Pinkerton started with detective work back in Scotland, and in 1849 he was appointed as the first police detective in Chicago. Year later he partnered with Chicago attorney Edward Rucker in forming the Detective Agency which became famous for solving a series of train robberies during the 1850s. Pinkerton produced numerous popular detective books, based on his own exploits and those of his agents.