Chae Woo-do

Set 3 years after the first season, members of the National Security Service (NSS) team, including Jung Yoo Gun, Ji Soo Yeon and other agents attempt to pull the curtain on mysterious group IRIS. Agent Yoo Gun is the leader of the NSS TF-A team. While he goes up against Baek San, Yoo Gun becomes involved in a case which changes his fate forever.

Sometime in the near future, the Korean peninsula attempts to reunify. The South Korean government, which needs enormous funds for the unification to succeed, develops a landmark new technology called the TWR. The TWR is a high speed nuclear reactor and other countries want the technology. To prevent terror in the aftermath of the TWR breakthrough, the government establishes a new organization named NTS (National Anti-Terror Service). Jung-Woo (Jung Woo-Sung) is transferred to the NTS group from the NIS. He's excited about the transfer and hopes to live the life of a real agent, but then discovers his main responsibility is to watch North Korean defectors.

Hyunjun and Sawoo, close friends and rivals from the South Korean special forces, are recruited by the secret agency NSS. They both fall for Seunghee, the beautiful but lethal profiling specialist at NSS. When they are faced against each other in a nuclear terrorist attack, they are forced to make their final decision and Seunghee's formidable secret is revealed.