This book is an examination of the everyday operations of the Gestapo, the Nazi secret police. How were the Gestapo able to detect the smallest signs of non-compliance with Nazi doctrines, especially `crimes' pertaining to the private spheres of social, family, and sexual life? How could the police enforce policies such as those designed to isolate the Jews, or the foreign workers brought to Germany after 1939, with such scrupulousness and apparent ease? Robert Gellately argues that the key factor in the `successful' enforcement of Nazi racial policy was the willingness of German citizens to provide the authorities with information about suspected `criminality'. He does not charge the nation with `collective guilt', but demonstrates that, without some degree of popular participation in the operations of institutions such as the Gestapo, the regime would have been seriously hampered not only inside Germany, but also in many of the occupied countries.