The film is based on the massacre Gwangju on May 18, 1980. It occurred when General Chun Doo-hwan tried to eliminate any rebels by using military force.
Min-woo leads a relatively peaceful life with his younger brother Jin-woo until the day the soldiers go on the rampage against the citizens. The citizens form a militia determined to protect their loved ones, and Min-woo finds himself in the middle of it all.
One day something unexpected happens suddenly. Innocent citizens are assaulted and even killed by martial law army armed with guns and knives.
A tear gas rolls into the theater and a college student jumps into the theater, followed by a soldier. When all the people who watched the movie came out, martial law soldiers beat up college students and beat everyone out of the theater.
Gwangju citizens, who have lost friends, lovers and family members in front of their eyes in an unjust manner, start to form a civic group centering on Heung-soo, who retired officer-turned-military officer, and begin a 10-day struggle.
Meanwhile, Jin-woo is angry that his classmate was beaten to death by martial law soldiers when he was not a college student, leading his friends to take the lead in the protest. Min-woo wants to stop his younger brother Jin-woo from taking the lead in the protest. But Jin-woo couldn't stay still, and in the end, Jin-woo was shot in front of Min-woo by martial law soldiers.
The governor of South Jeolla Province shows up on a helicopter to citizens in front of the provincial government to mediate between them. The broadcast was about to withdraw martial law troops until the hour of the day, and the civilian forces believe the words and cheer. Gwangju citizens wait for the right time, but the soldiers do not withdraw at the promised time. As the national anthem is played through the speakers of the provincial government building, citizens salute with their right hand on their left chests, while soldiers sit down and prepare to shoot in a posture at the civilians, and then fire away.