The central mystery revolves around uncovering the identity of the mole "Dong-rim" and halting an assassination plot. The film reveals that Park Pyong-ho is Dong-rim. Turned decades earlier as a North Korean intelligence asset, Pyong-ho gradually evolved into a moderate working to prevent regional war and secure peaceful reunification rather than conquest.
Simultaneously, Kim Jung-do is orchestrating a domestic military coup. Traumatized by his deployment to the 1980 Gwangju Uprising where he witnessed civilian massacres, Jung-do allies with dissident officers and a defense contractor to assassinate "Number One" during a state visit to Bangkok to atone for his guilt.
The central dramatic collision occurs when Pyong-ho learns that North Korea's military hardliners intend to exploit Jung-do's assassination plot by launching a full-scale invasion of South Korea the moment the President dies. To stop a devastating war, Pyong-ho is forced to thwart the assassination, placing him in direct conflict with Jung-do.
During the Bangkok summit ambush by North Korean commandos, Jung-do attempts to detonate explosives while Pyong-ho fights to foil the invasion trigger. Jung-do is mortally wounded by North Korean operatives, and the President survives. In the aftermath, Pyong-ho encounters Jo Yoo-jeong, who is revealed to be a sleeper agent tasked by Pyongyang with killing him. Pyong-ho gives her a forged passport and cash, urging her to live freely. When North Korean assassins ambush them and fatally shoot Pyong-ho, Yoo-jeong turns her weapon on the assassins, choosing her own autonomy and breaking the violent cycle.