KGB officer Major Valeri Petrofsky is sent on a mission to the United Kingdom by General Govorshin, the head of the KGB. Govorshin's subordinate, Pavel Borisov, complains to his old friend General Yevgeny Karpov, about his department being stripped of resources and personnel, particularly his star officer Petrofsky. A surprised Karpov quietly investigates and learns about Petrofsky's unsanctioned mission – to violate the Fourth Protocol by assembling and detonating an atomic device as a false flag, to appear to be an American nuclear accident at a nearby military base, intended to strain British-US relations and strengthen the anti-nuclear movement in advance of an election in favour of the Soviet Union.