A member of Coast Guard Platoon 23, Private Kang (Jang Dong-Gun) monitors a lonely stretch of beach on the Korean shoreline. Driven by the belief that killing a spy is the highest honor, he waits eagerly for a chance to prove his worth as a soldier. One night, Kang shoots without hesitation, mistakenly killing an innocent civilian. Despite receiving honors, he slowly begins to unravel under the grief of what he's done. Losing his grip on reality, tensions and paranoia escalate and further tragedy may become unavoidable.
