In 1944, Muriel Spark was recruited by the Foreign Office to work as a Duty Secretary in the Political Warfare Executive at Milton Bryan. ‘I played a very small part,’ Spark wrote in her autobiography, ‘but as a fly on the wall I took in a whole world of method and intrigue in the dark field of Black Propaganda or Psychological Warfare, and the successful and purposeful deceit of the enemy.’ Drawing on research in Spark's personal and literary archives at the McFarlin Library, Tulsa, and the National Library of Scotland, this essay explores the ways in which this ‘world of method and intrigue’ is taken in and reformulated in Spark's writing. Political espionage takes centre-stage in several of Spark's fictions, and a preoccupation with secrecy and spying runs through her work. But the methods of black propaganda can also be read as a secret sharer of some of Spark's most characteristic aesthetic strategies. Focusing in particular on Spark's most direct treatment of her secret war work – The Hothouse by the East River – critical tension centres on reading Spark's literary intelligence less as a re-enactment than as a subversion of the logics of disinformation.