One of the enduring mysteries of modern espionage is the Cambridge Spy Ring--the group that included Anthony Blunt, Kim Philby, Guy Burgess, and Donald Maclean--and the identity of the long-rumored sixth man. Many theories have been proposed over the years, yet no one has come forth with any irrefutable proof. And Sam Gaddis, an academic with a specialty in modern Russian history, is the least likely person to do so. Until an old friend reveals that she's working on just that story, suddenly dies; Sam's need for money becomes pressing, and he finds his way to someone claiming to have access to the real sixth man.

But the few remaining people with any direct connection to that sixth man begin dying unexpectedly, MI-6 begins tracking Gaddis trying to throw him off the trail, and he finds himself in the cross-hairs of a very real, very dangerous plot emanating from the highest levels of contemporary Russia. As Sam risks everything he has and everyone he loves to unravel the layers of secrets surrounding the identity of the sixth man, someone else is equally determined, for reasons unknown, to keep the details surrounding the long-standing deception surrounding the sixth man buried forever.