King Gwanghae (Lee Byung-Hun) has been the King for the past 8 years. He now suspects that someone within the royal court is attempting to poison him. In response, King Gwanghae orders his councilor Heo Gyun (Ryoo Seung-Ryong) to find someone that looks like him to sit in his throne.
Heo Gyun then comes across a clown named Ha-Sun (Lee Byung-Hun), who performs lewd shows in front of drunken noblemen. Ha-Sun indeed strongly resembles King Gwanghae and is even able to imitate the way King Gwanghae speaks. Heo Gyun takes Ha-Sun to the royal palace without giving any explanations. At night, Ha-Sun takes the King's seat, while the King slips away to his mistress's home.
A short time later, King Gwanghae collapses and is taken to a safe house. Meanwhile, Ha-Sun continues his ruse as the King until the King can recover. Slowly, Ha-Sun's own personality comes out and the people in the King's inner court notice the changes. The King appears more humane to those around him and far less volatile. While Ha-Sun's true voice comes out, enemies within the King's inner circle plan their next move.