John Limond Hart joined the CIA in 1948, serving as chief of operations in Korea, Thailand, Morocco, and Vietnam, managing operations against China and Cuba, and heading CIA operations in Western Europe from 1968 to 1971. He died in 2002.

During the Cold War a number of high-ranking Soviet citizens spied for the CIA, providing the United States with valuable information while putting themselves and their families in great danger. In this book a seasoned CIA field operator and station chief looks at what drove these agents to betray their own country. Unlike many authors who write about spies, John Hart knows the espionage profession firsthand, and his penetrating analysis of the motivations involved is based on top-secret operational files. Four major Soviet agents--Yuri Nosenko, the dissident KGB agent who disclosed the bugs in the American Embassy in Moscow and claimed the KGB had no connection to the assassination of President Kennedy; Oleg Penkovsky, one of the West's most important agents who was eventually executed by the Soviets; and Pyotr Popov and Mikhail--are examined in depth, and the cases of six others are discussed. The stories of each reveal a great deal about the realities of the intelligence craft.

Hart became so intrigued with the reasons behind the agents' spying activities that he asked then-CIA director Richard Helms for time off to investigate the cases. For a full year he searched for common denominators in the personalities of these Soviet moles that would explain their willingness to take such life-threatening risks. He had complete access to their operational files, including psychological profiles. He studied not only documentation of the material the agents provided but also their own accounts of their thoughts and emotions when they divulged secrets that could damage their homeland. Every reader with a penchant for good spy stories will appreciate this behind-the-headlines look at what makes spies tick.