The night watchmen of Joseon patrol the darkest hours of the day to protect the people from the evilest of all enemies. Ghosts, monsters, and supernatural forces abound and those who can see them, fight them. Lee Rin (Jung Il Woo) is the heir to the throne but chooses to lives his life as a watchman, as his father had once before him, rather than live in the palace. But when he sees the plight of his citizens under the rule of his tyrannical father, he learns that his gift can also be a curse if he lets the evil spirits take over him, and battles his way to becoming the rightful ruler of Joseon.