U.S. Marine veteran Mason Hackett moved to London to start his life over, and he's done his best to convince himself that what happened fifteen years ago doesn't matter—the people he killed, the men he lost, the lives he ruined. But when Mason sees the face of a dead friend flash on a television screen and then receives a mysterious email referencing a CIA operation gone bad, he can no longer ignore his inner demons.

Driven by loyalty and a need to uncover the truth, Mason launches on a perilous journey from the Czech Republic to Romania toward the war-torn separatist region in eastern Ukraine to honor a fifteen-year-old promise. The answers he seeks—the fate of a friend and his connection to the underworld of international arms dealers and defense corporations—throw Mason into the cauldron of a covert war where no one can be trusted.