The film, completed in 1981, remains a prototype spy film in the memory of the Korean people.

Produced against the Fatherland Liberation War (June 25, 1950-July 27, 1953), the film vividly depicted the sharp dramatic human relations, tight events and rich lyric atmosphere with compact scenario, direction, shooting, acting, narration and music.

It impressively shows the activities of prototype heroes who unhesitatingly devoted their youth and lives to the country.

The female leading part of the film was played by Kim Jong Hwa in her twenties, who had never acted in movies before. With this film she was recognized as a promising actress and, later, grew into a Kim Il Sung Prize winner and People's Artiste.

Kim Jong Hwa, now active as a teacher at Pyongyang University of Dramatic and Cinematic Arts, told KCNA:

My disciples would ask me how I could perform the leading part with brilliance at the film. Then I tell them that I made efforts only to truly represent the self-sacrificing spirit of a woman hero who held the destiny of the country dearer than her life.

Chairman Kim Jong Il initiated the production of this film with orchestra "Mind of Loyalty" as a theme and gave precious teachings on tens of occasions to complete the film into a masterpiece.

Amid the rapid progress in technical development for making black-and-white films into color ones, the monochrome film "Unknown Heroes" was turned into the first color one among the multi-part feature films.