London, 1921: Ex-Secret Service spy Jack McColl is in prison serving time for assaulting a cop. McColl has been embittered by the Great War, and can't stomach spying for the British Empire anymore. He's also heartbroken. The love of his life, radical journalist Caitlin Hanley, parted ways with him three years earlier so she could offer her services to the Communist revolution in Moscow. Then his former boss offers McColl the chance to escape his jail sentence if he takes a dangerous unofficial assignment in Russia. Little does he know, his mission will throw him back into Caitlin's life - while her husband is one of the men he is trying to hunt down.