Synopsis
Lifelong friends Kim Hyun-Jun (Lee Byung-hun) and Jin Sa-woo (Jung Joon-ho), two Special Forces soldiers under the South Korean army's 707th Special Mission Battalion, each independently come into contact with an alluring woman by the name of Choi Seung-hee (Kim Tae-hee). The pair do not at first realize they have fallen for the same woman and continue to aim for her affections. Soon afterward, they are ushered from their military base to a secret compound in the middle of the night.
There, they are subjected to extensive torture as a means of gauging their worth under the most extreme of conditions. After successfully completing the test, Hyun-jun and Sa-woo are introduced to the standing head of the National Security Service, Baek San (Kim Yeong-cheol). He informs them that the NSS is a secret organization tasked with preempting foreign threats and protecting the country's interests through wetwork operations including assassination of anyone who could be a threat to South Korean national security. Since its founding in 1976 during the rule of Park Chung-hee, the agency's very existence has remained a state secret from everyone, including the President.
Upon being initiated into the NSS, the pair learn individually that they had been headhunted by Seung-hee. Stirred by her deceit, Hyun-jun compliments her skills as an actress, while Sa-woo takes the news less bitterly. Still unaware that they share affection for the same woman, the two quickly prove themselves as capable agents within the NSS.
After taking on an unofficial assignment and foiling an assassination attempt on the leading presidential candidate, Hyun-jun and Sa-woo are invited to theBlue House. There, Hyun-jun experiences déjà vu, believing that he had stood in that very spot many years earlier.
Meanwhile, an elite assassin (T.O.P) appears at a high-rise hotel in Shanghai to eliminate a figure of political importance. After his bodyguards are disposed of, the man is killed and the assassin mentions his intention to move to the next and final target: Hong Seung-ryong, a defector from North Korea and the scientist heading their nuclear arms program.
As their personal relationships develop in unexpected ways, Hyun-jun, Sa-woo, and Seung-hee are soon sent to Budapest to secure Hong Seung-ryong while the Blue House decides whether to grant him asylum. Despite interference, they manage to deliver the defector to fellow agents tasked with escorting him to the South.
While their handover of Hong goes unheeded, a grand conspiracy begins to unravel at the hands of a far-reaching villain. As political tensions mount, Hyun-jun is given an independent assignment that will alter the course of history and change his life forever.
