Set 3 years after the death of National Intelligence Service (NIS) agent Kim Hyeon-Jun (Lee Byung-Hun), 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.