Shortly after the film's release, its final scene where the characters take a blood oath became a cult classic, and popularised the song "Kletva", which students began singing at their graduation proms.

At the end of the 1960s, Dana, the daughter of a diplomat in London, returns to Bulgaria and is enrolled in a boarding language school where mostly children of high party functionaries study.

Ivan comes from an upper class family, and even his serious offenses are forgiven, while Rostislav is admitted to the school on an academic merit basis, and even the slightest mistake can cause him to be expelled.

The young people are excited by the eternal themes of justice, love and friendship — humane ideas that challenge the prevailing totalitarian ideology.

Andonov agreed to do it under the condition that he would be allowed to include some of his own experiences from his student years in the script, in particular his fascination with the Beatles' 1968 self-titled album.

Andonov was impressed by director Nikola Rudarov's cameo appearance as the cameraman in the 1968 film One Shooting Day, and cast him in the role of the math teacher, Professor Baramov.

A drama student from the Academy was initially cast as Dana; however, Daverov insisted on Sofia Kuzeva playing the role, to which Andonov agreed.

The scene, in which he explains to his son why he was fired from the position of editor-in-chief at the magazine he worked for, was cut during editing, as it did not correspond to Andonov's creative vision.