Duel is a tense sci-fi thriller that follows Jang Deuk-cheon, a veteran detective whose daughter is kidnapped. In his desperate search for her, he encounters two identical men—one a cold-blooded killer and the other an innocent man suffering from amnesia. As Deuk-cheon realizes these men are clones, he becomes entangled in a dangerous conspiracy involving human experimentation and the pursuit of immortality. The narrative unfolds as a high-stakes cat-and-mouse game where the lines between hero and villain blur. Deuk-cheon must navigate a web of corruption and betrayal, relying on the amnesiac clone to uncover the truth about his origins, all while racing against time to save his daughter from a shadowy organization that will stop at nothing to protect its secrets.