Six CIA officers. Dear friends and cherished enemies. For a quarter century they have stolen other people's secrets. Now they must steal each other's.

A Russian arrives in Singapore with a secret to sell. When the Russian is killed and Sam Joseph, the CIA officer dispatched for the meet, goes missing, operational chief Artemis Procter is made a scapegoat for the disaster and run out of the service. Months later, Sam appears at Procter's doorstep with an explosive secret: there is a Russian mole burrowed deep within the highest ranks of the CIA.

As Procter and Sam investigate, they arrive at a shortlist of suspects made up of both Procter's closest friends and fiercest enemies. The hunt requires Procter to dredge up her checkered past in the service of the CIA, placing the pair in the sights of a savvy Russian spymaster who will protect Moscow's mole in Langley at all costs. What happens when friendships forged by sweat and blood—from the Farm to Afghanistan and the executive "Seventh Floor" of CIA's Langley headquarters—are put to the ultimate test? What can we truly know about the people we love the most?