Plot
In 1990, several children disappear into thin air. At the same time the Ministry of Defense has gathered leading scientists to proceed with a top-secret project. Thirty years later in 2020, Korea has been unified and retired scientists are murdered one after another. Top-notch equipment and SI agents are dispatched to investigate the scene. As if to mock them, the perpetrator leaves a pendant at the scene and even kidnaps the son of Seok, the leader of the SI team. Seok kills one of the perpetrator’s men, but ends up killing his own son, whom the man was holding inside his coat. Meanwhile, the chief of police is kidnapped in the middle of Intercity which was heavily guarded. The perpetrator leaves another pendant. Hui-su, daughter of the chief of police, who is also a criminal psychologist, joins the team. Seok finds that just like him, Hui-su has migraines, and can’t remember her childhood. A sudden thought occurs to Seok. Maybe the perpetrator had done all this so that he and Hui-su could meet each other. The lost memories of Seok and Hui-su, the formidable killing machine Goliath, the deaths of the scientists, all seem to be connected somehow, and the password is ‘yesterday.’