This book details Soviet espionage efforts, including the atomic espionage of Klaus Fuchs, in the United States from the 1930s through the end of World War II. The book's concern with all Soviet espionage efforts provides a context for Fuchs' and other atomic spies’ activities. How the Soviets successfully spied on the U.S. atomic project as well as what motivated Fuchs and other spies is detailed. Most of the information relevant to nuclear topics is in the fourth and fifth chapters. The author bases her book on declassified government documents from both the U.S. and Russia.