This exhibition is based on one of the most extraordinary collections held in the Hoover Library & Archives: the records of the Paris office of the Russian Imperial secret police, known as the Okhrana. The Okhrana collection, consisting of once-secret files and photographs of many of the most wanted Russian revolutionaries of the early twentieth century, documents the tsarist government's surveillance of its political enemies throughout Europe, including many who would become leading figures of the Soviet regime after 1917—most notably Vladimir Lenin, Leon Trotsky, and Joseph Stalin. Double Exposure displays the wide range of material used for intelligence gathering: surveillance reports from agents in the field, dispatches, lists of pseudonyms, ciphers, correspondence of revolutionaries, and countless photographs that became the principal tool for identifying surveillance targets.