In the shadow of the Cold War a letter from Oleg Penkovsky (Merab Ninidze) an agency of the Soviet Union received by MI6 stating the concern of Penkovsky about world safety and his anxiety about a nuclear war, So Emily Donovan (Rachel Brosnahan) a CIA Agent reached out to MI6 Agent Dickie Franks (Angus Wright) , who recruited British salesman Greville Wynne (Benedict Cumberbatch) to be their spy.