"Oldboy" tells the story of Oh Dae-Su (played by Choi Min-sik), a businessman who is kidnapped and held captive in a mysterious room for 15 years. With no memory of his past or the reasons behind his imprisonment, Oh Dae-Su must navigate his confinement and seek revenge against his captor. The film is known for its intense violence, dark themes, and intricate plot twists, which have captivated audiences and critics alike.