During the Cold War, a Soviet agent named Oleg Penkovsky writes to MI6, expressing his concerns about global safety and the threat of nuclear war. In response, a CIA agent named Emily Donovan contacts MI6 to enlist the help of British salesman Greville Wynne, who is recruited by agent Dickie Franks to serve as their spy.

The Courier
In the midst of the Cuban Missile Crisis, a British businessman is recruited by a secretive Russian contact to undertake a perilous diplomatic mission, aimed at preventing a global catastrophe.