This article analyzes Humphrey Slater's Conspirator (1948) as the first identifiable Cold War spy novel and uses textual analysis and new archival findings to place the novel into its proper historical and intellectual context. As a quasi-autobiographical confession, the novel predated The God That Failed in introducing its readers to the psychology and lifestyle of Western Communists in the 1930s and 1940s. Conspirator explores how new postwar strategic realities affected Soviet policies and helped to spur changes in the intelligence-gathering methods of the Soviet security apparatus. The novel's publication and its adaptation by Hollywood demonstrate the impact of British fiction on the process of constructing the image of a Cold War nemesis in the United States.