Set in historical era, an imperial investigator Wong Gyu is sent to an isolated and largely autonomous island, away from the Korean mainland, to solve a case of arson, but soon finds himself in the middle of a murder investigation. Wong's dogged investigation leads him to suspect that the murders are related to mysterious events that took place seven years earlier, in which the former owner of a paper mill was executed for Catholicism. The townspeople believe an evil spirit is responsible for their troubles, but as a rational man, Wong Gyu has no time for such superstitions. Soon, however, he is forced to re-evaluate his views as the string of gruesome murders continues to go unchecked. Despite his best efforts, he begins to understand why he was sent to investigate these crimes.
