The director Ryu Ho-son stated that his favourite scene was the one from the "Madonna Teahouse" in Part 5, in which former lovers Yu Rim and Kim Soon-hee each learn that the other is a North Korean agent.

[4] Unsung Heroes was also responsible for propelling American defectors James Joseph Dresnok and Charles Robert Jenkins to minor celebrity status in North Korea.

[5][6] Dresnok's popularity in his role was such that people in North Korea routinely referred to him as "Arthur," the name of the character he played in the film.

[9][10] The plot of Unsung Heroes is partially based on actual historical events during the Korean War, but many names and details were changed.

Initially, he only has three contacts in Seoul: Park Mu, the chief press officer for the Republic of Korea Army, Janet O'Neill, the wife of senior American intelligence official Dr. Kelton, and Lee Hong-sik, his handler, through whom Yu also runs into his old lover Kim Soon-hee, who is apparently employed by the United States Counter Intelligence Corps, and is introduced to Colonel Klaus.

Soon after, Lee is killed in a shootout with CIC agents, including Kim Soon-hee, leaving Yu unable to pass his crucial intelligence back to his government.

A waitress in that bar is subsequently arrested and tortured by Colonel Klaus, who learns that a man suspected to be Yu was seen making the phone call.

[1] Yu continues to gather intelligence on General Sin's coup attempt, this time passing messages back to Pyongyang by way of a radio operator disguised as a disabled veteran who begs outside hotels.

Colonel Klaus hears about a North Korean spy disguised as a veteran, and begins reviewing video tapes to check on Yu's activities.