Set 3 years after the death of NIS (National Intelligence Service) agent Kim Hyeon-Jun (Lee Byung-Hun) by terrorist group IRIS. At a warehouse that sells arms illegally, NSS (National Security Service) team leader Joon-Han (Sung Dong-Il) sees Detective Yoo-Gun (Jang Hyuk) and asks him to work with him as an NSS agent.

Later, Yoo-Gun is now a team leader for the NSS TF-A team. Soo-Yeon (Lee Da-Hae), who has loved Yoo-Gun since they were young, begins to work as an NSS agent as well. Choi Min (Oh Yeon-Su) is newly appointed as the NSS deputy director. Her only purpose is take down IRIS.

NSS ex-director Baek San (Kim Young-Chul) has been incarcerated at the NSS prison, located on a remote island. A helicopter requests to land on the island and identifies themselves as NSS agents. After landing, they suddenly open fire on NSS agents. They are actually IRIS members. They are led by Ray (David McInnis) and takes Baek San out of prison. But when the helicopter leaves the island, Baek San jumps out of the helicopter and into the ocean.

Yoo-Gun, Soo-Yeon and Hyun-Woo (Yoon Doo-Joon) arrive on the island. Soo-Yeon is caught by Baek San, who points a gun at her. Yoo-Gun tries to mediate with Baek San, but Hyun-Woo fires from long range towards Baek San. Soo-Yeon is shot and taken to the hospital.

Baek San is moved to a NSS secret house. There, Baek San is interrogated by Yoo-Gun. He wants to know why he turned himself in and why IRIS tried to take him, but Baek San stays silent. Baek San only asks for 3 newspapers to read daily. The NSS team tries to find any secret code hidden within the newspapers, but find nothing.

At this time, IRIS members approach the NSS secret house. A gun fight erupts between IRIS and NSS agents. Yoo-Gun takes Baek San out of the secret house and runs to a car with Baek San. IRIS chases after the car with Baek San. Yoo-Gun is able to get to a military base and they are temporarily safe from IRIS. Yoo-Gun and NSS deputy director Choi begin to suspect that there's an IRIS mole within the NSS ranks.

Baek San finally reveals to the NSS agents that IRIS may launch an attack in Hungary, where high level meetings between North and South Korea are about to take place. He's unsure if IRIS is targeting North or South Korea.

Meanwhile, Soo-Yeon is now recovered. Even though Yoo-Gun opposes, Soo-Yeon goes to Hungary with the NSS team. Meanwhile, Yeon-Hwa (Lim Soo-Hyang) from IRIS arrives in Hungary and plots out their scheme. There's also Joong-Won (Lee Beom-Soo), who escaped from North Korea, and appears in Hungary by Yeon-Hwa's request.