We think we know all the Cold War's greatest spy stories. The tales of America's greatest traitors have been told over and over. However, the biggest story of them all remains untold--until now. Rumors have long swirled of another mole in American intelligence, one perhaps more damaging than all the others combined. Perhaps the greatest traitor in American history, perhaps a Russian ruse to tear the CIA apart, or perhaps nothing more than a bogeyman, he is often referred to as the Fourth Man.

Blowing the lid off the biggest spy story in decades, Robert Baer tells the full, gripping story for the first time. After arrest of KGB spy Aldrich Ames, the CIA launched another investigation to make sure there wasn't another double agent in its ranks. Led by three of the CIA's best spy hunters, women who devoted their lives to counterintelligence, its existence was known only to a few. They began methodically investigating their own bosses and colleagues, turning up loose threads, suspicious activity, and shocking intelligence from the CIA's best Russian asset. In the end, they came to a startling conclusion that, whether true or not, would shake American intelligence to its core, setting the stage for a cat-and-mouse game with enormous geopolitical stakes. Spies and moles may seem like bygone cold war history, but with Russia again a misunderstood belligerent power, the skeletons America would rather keep hidden are emerging, and as Robert Baer shows in this thrilling masterwork of investigative reporting, they matter as much now as ever.