For all the attention historians have paid to the intrigues and drama involving intelligence agencies during the Cold War, the story behind those stories—the inner workings of state institutions, the people who ran them, and the changes they underwent—has remained largely opaque. Haslam takes seriously the task of tracing the history of Soviet espionage, to the extent that old and new sources allow. He acknowledges the significant obstacles that stand in the way, but his book fills in some large gaps. It covers the Soviets’ often bumbling early intelligence efforts in the years immediately following the 1917 Russian Revolution, as well as the increasingly professionalized operations of the 1920s and 1930s, when the Soviets “turned” Western leftists to the cause until Western intelligence agencies caught on and began dismantling the Soviet network after World War II. He reveals a striking divide between the 1930s and the post-Stalin years: in the earlier era, Westerners who allowed themselves to be recruited to the Soviet side were often idealistic; in the later years, such recruits were more frequently merely venal.