After his partner is killed, Gun Woo joins the elite undercover unit the Criminal Investigation Team and goes deep undercover to recover an old friend.

Though Gun Woo is suspected of being a cop, the gang brings him along on a job. The Criminal Investigation Team finds Hae imprisoned by the gang, but he insists on staying to complete the mission.

Min Tae In finds a way to extract himself and prove Gun Woo's loyalty. Complications ensue as as the criminals attempt to steal the hologram.

Gun Woo officially joins the team and puts his investigation skills to use as they track a hacker known as the Mermaid.