1990. A number of children suddenly disappear. Meanwhile, the Ministry of Defense selects an elite group of scientists for a top-secret mission. Then, 30 years later … The year is 2020 on a reunified Korean Peninsula. A string of murders is committed against retired scientists. The Special Investigations (SI) unit staffed by a crack team from the former North and South Koreas and outfitted with the latest technology is brought in to investigate. The killer, however, far from being deterred, taunts them with a signature pendant at every murder scene. In an act of devilish boldness he even kidnaps the son of the investigation team’s leader, Seok. Then, in a stakeout, Seok manages to shoot dead one of the murderer’s underlings. Cloaked in the man’s clothes, however, is Seok’s son, now dead by the hand of his father … Meanwhile, in the megapolis Intercity, the chief of police is kidnapped right in front of his heavy security detail and the culprit leaves another pendant at the scene. The chief’s daughter, Heesu, a talented criminal psychologist quickly joins the investigation to find her father. Soon, Seok discovers that he and Heesu share an uncanny bond…