Two North Korean soldiers are killed in a shootout at the Joint Security Area
in the DMZ between North and South Korea. A wounded South Korean, Sergeant Lee Soo-hyeok (Lee Byung-hun) makes it back across the border alive. A Swiss-Korean UN officer, Major Sophie Jean (Lee Young-ae) is sent to investigate this delicate international incident. She uncovers a strange story involving an encounter between the South Koreans at a guard post and the North Koreans at the opposite guard post, and she interviews a North Korean survivor, Sergeant Oh Kyeong-pil (Song Kang-ho).
The film contains examples of:
- All for Nothing: Sophie’s superior officer even admits this to her before the climax; both South and North Korea actually want the investigation to prove nothing at all, and called in a third party as mandated by the armistice to uphold the appearance of neutrality and maintain the status quo.
- Anachronic Order: The movie starts after the shoot-out has taken place, then in its middle tells the story behind it and eventually takes up the first narrative level.
- Anti-Villain: Oh Kyeong-pil has no regrets about supporting his country's rigid, cruel regime, and is loyal to Kim Jong-il, but he has no regrets about the situation either. He grows to love Soo-hyeok like a brother, and goes out of his way to protect him and Sung-shik when the shootout occurs, even when he takes the blame off of killing the commanding officer to save himself.
- Artistic License – Military: Oh is referred to as jungsa (a senior NCO in the Korean People's Army) throughout the film, however the epaulets on his uniform show that he is a sanggup pyongsa (a mid-level NCO).
- Ate His Gun: After confessing the truth to Major Jean, Lee has a flashback of him shooting Jung and does this after attacking and disarming his MP escorts.
- Back to Front: The story is told backwards, and the title cards for each act reflect this: Act I is titled "Area", Act II is titled "Security", and Act III is titled "Joint".
- Binocular Shot: Seen from the POV of Sophie's superior officer, as he looks at the North Korean side from the south.
- Call-Back:
- One of the other South Korean soldiers in Soo-hyeok's unit talks about what a badass he is, and says how one time when he was out on patrol in the DMZ he stepped on a land mine but disarmed it himself. A later flashback reveals that in fact it was Oh and another North Korean soldier, Jung Woo-jin, who found him with his foot on the mine and saved him.
- Early in the film, a tourist on the southern side of the JSA loses a hat in the wind, which blows over to the northern side. Kyeong-pil hands the hat back, and the sound of other tourists snapping photos is heard on the soundtrack. The very last shot of the film repeats that scene, but shows the photo the tourist snapped, which as it turns out included all four of the main characters.
- Chalk Outline: There's a chalk outline showing where a body fell directly on the border line, and two more, with accompanying splatters of blood, showing where two soldiers died in the North Korean guard hut.
- Chekhov's Gun: Jung is shown to be a talented artist. It's later revealed he drew a picture of Lee's girlfriend based on a photo that Lee left in the guard shack, providing a crucial clue to what really happened.
- Chekhov's Gunman:
- Nam, who is initially another unimportant guard; after attempting suicide, he is revealed to have been sneaking over the border too, and to be the second shooter.
- Lt. Choi, the North Korean officer who comes into the guard shack one night and yells at Oh and Jung for hanging out in the basement (they were actually hanging out with Lee). He makes another visit to the guard shack at the worst possible time, triggering the violent climax.
- Dead Man's Trigger Finger: Jung gets shot through the head by Nam (later revealed to have actually been Lee), and as his dead body is falling backwards, his gun goes off and shoots Lee in the leg.
- Dirty Coward: Nam sprints back across the border after everything goes to hell, leaving Lee behind.
- Driven to Suicide: Both South Korean soldiers: Nam throws himself out of the window when threatened with a lie-detector test; and Lee shoots himself after explaining everything. Nam presumably survives, but Lee definitely does not.
- Every Scar Has a Story: In an effort to intimidate Sophie, Oh shows her the scars he received from action in North Africa.
- Faux Fluency: It's clear Lee Young-ae learned her English lines phonetically. Later versions completely dubbed her lines with a native English speaker.
- Foregone Conclusion: The friendship between the soldiers will end badly.
- Grey Rain of Depression: When Sophie is removed from the case.
- How We Got Here: A Swiss-Korean officer is sent to the JSA to investigate a shooting. The story plays out in a series of flashbacks.
- Hypocritical Humor: Oh, a loyal North Korean soldier, admits that he loves "Yankee shit" like Zippos.
- In Medias Res: The film starts with a scene showing the lonely shack at the end of a bridge—and two shots are fired. The rest of the story tells what happened.
- Interrogation Flashback: The film is told largely in flashbacks, with a Framing Device of a UN officer interrogating soldiers involved in a fatal shooting incident at the DMZ.
- Land Mine Goes "Click!": How Soo-hyeok met the North Koreans. He was on patrol in the DMZ, stopped to take a pee, and realized afterwards that his foot had caught the tripwire to a mine. The two North Korean soldiers disarm the mine and save him.
- Match Cut: There's one from an umbrella to one of the watchtowers' identically shaped roof.
- Model Planning: After the fact. When Sophie finally gets Soo-hyeok and Kyeong-pil together in a room (the conference room at the border of the JSA, in fact), she busts out a model of the North Korean guard shack in an attempt to get them to confess what really happened.
- Not Even Bothering with the Accent: When speaking English as Sophie E. Jean, Lee Young-Ae doesn't try to mask her Korean accent even though she's playing a Swiss character.
- The Place: The Joint Security Area of the Korean DMZ, the one place where the two opposing forces come in contact.
- Ominous Owl: The very first shot is a close-up of a staring owl, establishing an ominous mood.
- Overcrank: Done for aesthetic purposes in the shoot-out at the end.
- "Rashomon"-Style: Though there is also a great deal of additional investigation besides the interrogations.
- Reveal Shot: When Lee tells Sophie the truth, the camera zooms in on his eyes. It then zooms back out to show a flashback of what really happened.
- Shown Their Work: With a highly accurate recreation of the Joint Security Area. As of 2015, the JSA set still stands.
- Sins of Our Fathers: Sophie's father was originally a North Korean Army officer who refused repatriation to North Korea (or an offer to emigrate to South Korea) after the Korean War. He ended up going to Argentina and marrying a Swiss woman, leading to Sophie's birth. General Pyo (the South Korean general at the DMZ) digs up this information and has her removed from the investigation because of this, as he feels it might somehow compromise her neutrality (and embarrass South Korea).
- Survivor Guilt: Lee. He ultimately blows his brains out after it's revealed he was the one who fired the fatal shot to Jung, not Nam.
- Take It to the Bridge: The famed "Bridge of No Return".
- Toilet Humor: Woo-jin farts as a practical joke.
- Truce Zone: The Korean Demilitarized Zone during the aftermath of a murder in which it appears that a South Korean soldier killed his North Korean counterpart.