Kyeong-Yoon (Kim Kang-Woo) and Eun-Ju (Kim Gyu-Ri) investigate a grisly murder of an affluent entrepreneur. The victim was slashed over 20 times and thereâ€™s blood everywhere in his apartment. The killer was careful not to leave behind incriminating evidence, but nevertheless, a strand of the killerâ€™s hair is found. The police are then able to determine that the killer is male and has AB bloodtype.
Shortly after the first grisly murder a second murder occurs. The victims seem to be unrelated but the modus operandi seems the same. When the police delve deeper into the victimsâ€™ background they discover that the two victims were stationed at the same military base many years ago. A month prior to their discharge they were transferred to another base along with a third man by the name Jay Bae. The police now believe Jay Bae could be the next victim or the killer. Their investigation has only just begun.