Ten years ago, a tragic incident occurred in the heart of Seoul where a teenage girl was murdered. Detective Go Tae-seong (Park Jae-hong), who took on the case, couldn't find even the slightest clue to the perpetrator, and the case was eventually closed as unsolved. Ten years later, when another high school student is abducted, Go Tae-seong instinctively sets out to find the culprit.