Private Kang, played by Jang Dong-gun, is a South Korean marine stationed along the coastline near the Korean Demilitarized Zone. He is portrayed as intensely eager to neutralize perceived threats, sometimes with a reckless edge that blurs the line between vigilance and aggression. On a dimly lit night, a drunken local couple trespasses into the fenced-off zone seeking privacy. From the glow of his night-vision scope, Kang spots the man and, mistaking him for a North Korean intruder, fires with rifle and grenade. The fatal mistake triggers a chain reaction of guilt, fear, and unsettled nerves that ripple through the lives nearby and haunt Kang himself.
The aftermath spirals into a complex web of trauma. The dead civilian’s girlfriend, overwhelmed by the sudden violence and her own fragile state of mind, becomes convinced that the coastal guards are somehow connected to her lover’s death and starts forming intimate, destabilizing connections with members of the unit. She becomes pregnant, and the pregnancy ends in a botched abortion carried out by the unit’s medics, whose incompetence compounds her pain. Her brother reaches a boiling point, his anger driving him to attempt violence against the guards, only to be restrained by local police.
In the wake of the incident, Kang is publicly commended for his action and granted a period of leave. Yet the celebration masks the onset of post-traumatic stress disorder—nightmares, flashbacks, and a growing emotional numbness. His friends begin to distance themselves, and his relationship with the woman who loves him deteriorates as she leaves. When Kang returns to duty, he encounters hostility from those connected to the dead man, and the scars of his PTSD deepen. After a series of troubling episodes, the military evaluates him as mentally unfit for service and discharges him honorably. Kang refuses to walk away, and his attempts to rejoin fail; he personifies a fracture line in the system by stealing military equipment and turning his anger against his own squad.
Driven by a fractured mind and a sense of injustice, Kang moves to Seoul’s Myeongdong, where the violence escalates as he begins to stab people at random with a bayonet. The situation crescendos when he is confronted by armed police, and a tense gunfight erupts as authorities try to stop him from causing further harm. The film closes on an uneasy note, portraying the corrosive effects of trauma, miscommunication, and the human cost of conflict on both personal and communal levels.
