As guardian of the security of the new Bolshevik regime after 1917, the Cheka dispensed revolutionary justice, combatted rival parties, and brought official terror, espionage and counter-espionage to a new level of proficiency. Using recently published Soviet material and other sources, Leggett comes as close as a Westerner can get, given still existing handicaps, to a definitive history of this institution and its sinister chief, Feliks Dzerzhinsky.