This national bestseller provides a riveting account of Adolf Tolkachev, a Soviet engineer who became one of the CIA's most valuable spies during the final years of the Cold War. Drawing on previously classified CIA documents and interviews with firsthand participants, the book delves into Tolkachev's courageous espionage activities, the immense risks he and his handlers faced, and the profound impact of his intelligence on U.S. military technology and strategy. PENGU