During the confusing and conspiratorial Joseon Dynasty King Gwang-hae orders his councilor, HEO Kyun, to find him a double in order to avoid the constant threat of assassination. HEO Kyun finds Ha-sun, a jester who looks remarkably like the king, and just as feared, Gwang-hae is poisoned. HEO Kyun proposes Ha-sun fill the role as the king until Gwang-hae recovers fully and grooms Ha-sun to look and act every bit the king. While assuming the role of the king at his first official appearance, Ha-sun begins to ponder the intricacies of the problems debated in his court. Being fundamentally more humanitarian than Gwang-hae, Ha-sun’s affection and appreciation of even the most minor servants slowly changes morale in the castle for the better. However, his chief opposition, PARK, notices the sudden shift in the king’s behavior and starts to ask questions.
Sung-Bum (Uhm Tae-Woong) is a hot-tempered detective who relies on his intuition to crack cases. He rarely comes across a case that he cannot solve. The body of a police officer is then discovered in a burned out car near an abandoned building. Drugs are also found near the dead officer. To catch the killer the police department sets up a special investigation unit for the case. Sung-Bum takes part in the investigation. Ho-Ryong (Joo Won) is a young, confident man who works as a criminal profiler. He trained with the F.B.I. in the United States. Ho-Ryong is also assigned to the special investigation unit. Ho-Ryong relies on evidence rather than instinct. Detective Sung-Bum takes an immediate dislike for Ho-Ryong.
Pastor Park is head of a religious investigation center that exposes cults and cult leaders. While looking into a suspicious new religion called ‘Deer Mount,’ he slowly uncovers clues that connect this cult to a series of mysterious cases of missing teenage girls when a body is found inside a damaged tunnel beams. He begins to uncover dark secrets surrounding this cult and its enforcer Na-han.