This monograph for the first time comprehensively assesses the historiographic and source study possibilities of studying such an urgent topic as the history of the Soviet state security agencies. The author identifies in the research literature on the Cheka-NKVD both an objective component and a mythology designed to embellish the criminal aspects of Chekist work - terror, provocative methods of using agents, and criminality of personnel. A significant place is given to the critical analysis of the points of view on the history of "organs" proposed by foreign historians. An analysis of the source study base proves the rich possibilities of finding information about Chekist work and personnel not only in official documents of the Cheka-NKVD from departmental and party-state archives, but also in newspaper chronicles, memoirs and even fiction. The book is designed for specialists, students and graduate students engaged in research of Russian history of the twentieth century.