In this era of email intercepts and drone strikes, many believe that the spy is dead. What use are double agents and dead letter boxes compared to the all-seeing digital eye? They couldn't be more wrong. The spying game is changing, but the need for walking, talking sources who gather secret information has never been more acute. And they are still out there. In this searing modern history of espionage, Stephen Grey takes us from the CIA's Cold War legends, to the agents who betrayed the IRA, through to the spooks inside Al-Qaeda and ISIS. Techniques and technologies have evolved, but the old motivations for betrayal — patriotism, greed, revenge, compromise — endure. This is a revealing story of how spycraft and the 'human factor' survive, against the odds.