The film is dedicated to the uprising, which broke out in Bulgaria in September 1923. All characters, with the exception of the leaders of the uprising Georgi Dimitrov and Vasil Kolarov, are symbolic characters. The central figures, Stefan and Peter, impersonate the motive forces behind the uprising - the workers and the peasants. They are involved in worker's strikes, in the stormy events of the First World War and the Soldier's uprising in 1918. They also participate in the bloody clashes of the September uprising and suffer its defeat after they have seen too late the need for concerted action by communists and agrarians.
The action takes place in the last years of the Second World War, immediately before the socialist revolution in Bulgaria. It centers on the life of the middle-class family of Lazarov, which is torn by the sharp political contradictions taking place against the background of the popular struggle against fascism. The father Vitan goes through terrible mental traumas, which are the price, he has to pay for his illusions that in such clashes one can remain neutral and free from politics. The partisans execute the son Boris - a fascist officer, a sadist and a murderer. The daughter Lily is forced to search for her place in the conflict between the representatives of two hostile worlds - that of fascist brother and her husband - a communist and a revolutionary.
Constantinople, 1883. During an outing to the Black Island Edith, the adopted daughter of the French ambassador, is saved by Kalin the Eagle. She learns that he is a Bulgarian revolutionary from the April Uprising of 1876. With her help Kalin the Eagle escapes and returns to the liberated Bulgaria, where he is drawn to the socialist movement. Edith finds out that Kalin is in fact her father, and sets out in search of him. Kalin the Eagle is notable as the first movie made by the nationalized film industry after World War II in the newly formed People's Republic of Bulgaria.
