For one year spanning 1955 and 1956, British and U.S. intelligence services were able to—literally—tap into top-secret Soviet and East German military communications. Engineers dug a tunnel a quarter of a mile in length from the U.S. zone of divided Berlin to the Soviet zone in order to splice into underground communication wires. Intelligence historians have traditionally claimed that what was called Operation Gold produced no information of value because George Blake, a Soviet mole in British intelligence, warned the KGB about the project before it even began. According to this view, the Soviets would not have allowed conversations of any substance to be intercepted. In this riveting and vivid account of the episode, Vogel demonstrates convincingly that a lot of valuable information was in fact obtained from the tunnel, largely because the KGB wanted to protect Blake from exposure and so decided to maintain the fiction that the Soviets were oblivious to the intrusion. At the heart of the book is Blake’s own remarkable story, which Vogel tells with some sympathy, if not approval. It reads like a Hollywood screenplay: a young Dutchman escapes the Nazis; joins the United Kingdom’s Secret Intelligence Service, or MI6; is captured by North Korean forces during the Korean War; and decides, while in captivity, to become a Soviet agent. In that role, Blake was responsible for many betrayals. Eventually, he was caught, tried, and jailed, before escaping from prison in London and making his way to Moscow—where he still lives on a KGB pension.