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