The action takes place in the sixties, during the Cold War, when one of the main means of struggle between two hostile political systems was espionage. The head of the British residency in East Berlin, Alec Limas, after the death of one of his main agents, a member of the SED, Karl Rimek, responds to London and is threatened with retirement. It is believed that in the fight against East German intelligence, whose operations department is led by Hans Dieter Mundt, Limas lost, losing all his best agents.
However, the British intelligence leadership gives Limass one last chance - to take part in a risky operation to discredit Mundt in the eyes of the GDR government as an agent of London. Limas is allegedly fired for retirement, and for some time he erases a miserable existence, drunk. Limas knows that sooner or later Mundt’s people will establish contact with him, because, as a former intelligence officer, he has valuable information that foreign intelligence will pay a lot for, and Limas is poor. In the operation, the beloved of Limasses, a member of the British Communist Party, Elizabeth Gold, is also drawn into.
Mundt’s people contact Aimas and offer him to move to Holland, where he can tell them everything he knows and get a large sum of money. In Holland, he meets with the German intelligence officer Peters, who elicits from Limas all the details of intelligence work. Limass's goal is to provide information that Chef Mundt Fiedler, who hates his subordinate, could use for his own purposes. To meet with Fiedler, Limas is eventually transferred to the GDR. Limas makes it clear to Fidler that British intelligence has a very valuable agent in this country with whom London maintains direct contacts and whose name Limass does not know. It may well be Mundt, who was previously a resident of East German intelligence in London and miraculously slipped away after his failure when he was wanted throughout England. This strange episode in his biography attracts the attention of Fiedler, who has long been collecting incriminating materials on Mundt.
During conversations with Fiedler, the question arises: what do both warring systems see as justification for their actions? Fidler justifies any crimes by the fact that the socialist system is defending itself against counter-revolution, that there can’t be absolute justice in the struggle for peace and progress, that intelligence is a weapon in the hands of the party, etc. Limas’s answers are not so categorical, but it’s clear that the end justifies the means, although Limass himself is far from cynicism in contrast to Fiedler. He is already tired of the endless struggle and wants to return home to England.
However, Mundt learns about Fidler’s machinations and arrests him and Limas, the latter at the time of his arrest in the fray kills the guard, and now he must be tried according to the laws of the GDR. Mundt interrogates in Limas prison, but at the last moment Fidler appears, who submitted his materials to the Presidium of the State Council and found support there. Mundt was arrested and will be tried by a tribunal appointed by the Presidium, Fidler will be the prosecutor, and Limas will witness the prosecution. Mundt will be defended by the well-known lawyer Carden, who is going to present an unknown defense witness to the court. This witness is Elizabeth Gold, who, without suspecting anything, comes to the German Democratic Republic at the invitation of the German Communists. From her testimony, Carden extracts information indicating that British intelligence is behind Limass - after the disappearance of Limass, some people came to Elizabeth, she received a significant amount of money from whom, etc. Limass made a mistake in contacting this woman - She knew too much, without understanding anything about what was happening. Limas misled Fiedler, who was trying to discredit Mundt, an honest member of the party, - Carden and the entire tribunal came to this conclusion, believing that the machinations of Western agents were exposed. Limas recognizes this, only at the last moment guessing what the true plan of his chefs, headed by the famous Smiley, consisted of. Mundt is acquitted, and Fidler will face punishment - this is exactly what they sought in London, because Mundt was the very important agent whom, without knowing it, Limass hinted to Fidler. At the same time, Limas and his beloved were used for their purposes by British intelligence, and then Fiedler to remove Mundt and, finally, the court of the German Democratic Republic supposedly to expose the intrigues of the enemy, who, in fact, in the face of Mundt comes out of the water and helps Limas and Elizabeth to escape from jail. However, both of them are no longer needed by anyone - the warring systems used them, and the heroes die, shot by border guards at the time of crossing the border into West Berlin. Such is the fate of a particular "little" man who was destroyed by the millstones of the hellish Cold War machine.
