The story takes place in Joseon period, when power struggles surrounding the throne had reached extreme levels. In order to escape those who plan to assassinate him, the King puts a clown, who looks exactly like him, on the throne.

Joseon is in disorder from uprisings and a power struggle surrounding King Yi Heon. To avoid assassination, a clown named Ha Sun is brought to the palace to take the place of King Yi Heon. Ha Sun looks almost identical to King Lee Hun. When Ha Sun was a child, his parents died during an epidemic; he was saved from starvation by a group of clowns and became one of them when he grew up, and during their performances he would play King Yi Heon, whom he greatly resembled. Now Ha Sun is nervous that someone in the palace will discover that he is not the real king. Meanwhile, he falls for the beautiful Queen Yoo So Woon. ~~The drama adaptation of "Masquerade", is a story that takes inspiration from "The Prince and the Pauper" by Mark Twain. (Source: AsianWiki, HanCinema)—MyDramaList