Greville Wynne (Benedict Cumberbatch) is a British businessman and MI6 spy under cover who is involved in a delicate CIA operation during the Cold War. Together with his Russian source and partner, Colonel Oleg Penkovsky (codenamed 'Ironbark'), they manage to secure intelligence that helps CIA access the nuclear program of the Soviet Union. Thanks to crucial information, provided by Wynne and Penkovsky, the Cuban Missile Crises, also known as the October Crisis of 1962, comes to an end. It has been caused by a confrontation between the United States and the Soviet Union, after the Americans discovered that Soviet ballistic missile has been deployed in Cuba. The confrontation between these two great powers is often considered the closest escalation of events that might have lead into a true nuclear war.