Set in the era of Joseon dynasty the series revolves around Sung Yi Kyum (L), a state examination top scorer who works in the administrative and research department of the government office. He is caught gambling and as punishment, he is re-assigned to a new position as a secret royal inspector to investigate the corrupt practices of public officers. Yi Kyum carries out his new job with the help of Hong Da In (Nara), a female inspector, and Park Chun Sam (Lee Yi Kyung), his talkative but affectionate servant.