Thrown straight into a dangerous mission with none of his memories intact, a man must escape death while trying to figure out who he is, how he ended up here, and who is the mysterious voice in his ear calling him "Carter"?
Carter, who awakens two months into a deadly pandemic originating from the DMZ that has already devastated US and North Korea. He who has no recollections of his past finds a mysterious device in his head, and a lethal bomb in his mouth. A voice in his ears gives him orders to avoid getting killed and he's thrown into a mysterious operation while the CIA and North Korean coup chase him close.
In the midst of a deadly pandemic caused by a virus which makes the infected patients violent and zombie-like, originating from the DMZ that has already devastated the United States (150K infected and 30K dead) and North Korea (8.5 M infected and on the verge of collapse), a man wakes up in a blood-soaked bed in a motel room in Seoul, with a cross-shaped scar on the back of his head. He is intruded upon by armed CIA agents who threaten him to ask the whereabouts of Dr. Jung Byung-ho (Jung Jae-young). Dr Jung and his daughter have been missing for 19 days, as reported on the news, on their way to North Korea.With no recollections of his past, he doesn't know who he is or why he is there, let alone who Dr. Jung is. A female voice inside his ear which only he can hear, tells him that his name is Carter (Joo Won) and he needs to follow her instructions if he wants to live. Following the voice, he escapes the room and enters a public bath where he confronts hundreds who try to kill him but survives thanks to his fighting and killing skills.
Inside a van of NIS agents (Strategic agents of North Korea) Choi Yu-Jin (Byeon Seo-Yun), the female voice reveals that she is Han Jung-Hee (Jeong So-Ri) who works for North Korea's Labor Party, which is working with South Korea to create a treatment for the virus. Dr. Jung Byung-ho, who successfully cured his own infected daughter Ha-Na (Kim Bo-Min), leads the project based on an antibody from her. On the way to a lab in North Korea (where North had made large scale preps to produce 100 MM vaccine shots), Ha-Na & Dr Jung went missing and was presumed to have been kidnapped by CIA. North is blaming South for this kidnapping, as a conspiracy to destroy the North's infrastructure.
Carter is tasked with rescuing Ha-Na and bringing her back to North Korean facility where the production of a vaccine is underway. When Carter questions his identity and why he is engaged in this mission, he is told that he is a South Korean (A CIA agent)-born naturalized citizen of North Korea (Carter fell in love with a North Korean woman and married her) who has decided to take part in the mission to save his infected daughter (she is also imprisoned in North Korea). they say, He was the one who commanded to have his memory center blocked. Carter is taken to the building where Ha-Na has been imprisoned.However, CIA agents who approach him claim that he is actually a former CIA agent named Michael Bane who was believed to be dead during a mission in Syria. Jung-Hee allows her signal to be tracked to Carter's molar, and the CIA takes the molar out. Jung-Hee tells Carter that the molar will explode in 5 secs, giving him an opportunity to escape.
They hide among the crowds in the streets and watch the news that says that Dr. Jung Byung-ho has managed to reach the research facility in North Korea. Agent Agnes (Camilla Belle) approaches Carter and asks him to trust her (she blocks Jung-Hee's signal to Carter), but she is shot. Ha-Na is kidnapped by the CIA and Choi Yu-Jin tries to save her. Choi Yu-Jin is killed, but Carter reaches in time to save Ha-Na. Meanwhile using Agnes's earpiece, Carter knows that CIA has established his identity as Michael Bane and are preparing to kill him. Carter eliminates the entire CIA squad. Jung-Hee guides Carter to an airstrip and onto a plane to North Korea.
The troubles are not over yet, as the pilots on the plane are given coffee that infects them with the virus. It was the North Korean medic on the plane who was trying to kill Ha-Na and Carter by luring them to the cargo hold. Director Kim is in charge of security on the plane (he is South Korean), and he shoots the medic to save them both. He questions the medic about who created the virus, since it can lead to a coup against the current regime in North Korea. The medic admits that he is working for the CIA, just like Carter. Kim is killed in the shoot-out. The medic triggers an explosive, which rips a hole in the plane. The medic returns to the main area of the plane and tells both the South and North Koreans that Kim was working for the CIA and tried to kill Ha-Na.Before this can be sorted, the infected pilots attack the main area of the plane. The medic uses the confusion to try and escape with a parachute and Ha-Na, but Carter was still in the cargo hold. As the medic jumps, Carter goes after him (without a parachute). He takes Ha-Na and the parachute mid-air and lands safely.On the ground, Carter is again attacked by CIA teams, and Carter has to fight them off. Carter is then attacked by hordes of zombies, whom he shoots, before escaping.
Nevertheless, Carter manages to arrive North with Ha-Na, where they meet Han Jung-Hee and her superior North Korean General Kim Jong-Hyeok (Lee Sung-Jae). When he is at the edge of completing his mission and getting his memories back, he and Jung-Hee are betrayed by a North Korean military coup led by General Kim. General Kim refuses to let Carter leave, since the deal was made by the Party and not him. Kim plans to use the virus to destroy South Korea and the US, so he can create a new world order (with the vaccine in his control).
While Ha-Na is in the possession of military, General Kim convinces Jung-Hee to join the coup. Carter escapes from Kim's soldiers who try to kill him. Carter follows General Kim and Jung-Hee to a bio-medical facility where Ha-Na is being taken, reuniting with her father Dr. Jung Byung-ho. Carter learns that Jung-Hee is his wife and shoots Kim who threatens Jung-Hee with a gun. At the same facility, they meet their infected daughter Yoon-Hee who behaves violently and transmits the disease to her mother Jung-Hee. Dr. Jung Byung-ho injects Yoon-Hee an antidote which makes her temporary unconscious.
After fighting against the infected patients and Kim's soldiers, they escape the facility on a jeep. The five; Carter, Jung-Hee, Yoon-Hee, Dr. Jung and Ha-Na departs to catch a train operated by Chinese government, carrying infected people to Dandong, China. Jung-Hee says that they need to stop the train, else the virus will spread globally. On the way, Jung-Hee and Dr. Jung Byung-ho get Carter's memories back by activating a device back on his head. Carter remembers that he agreed on this mission in exchange of his family's freedom (They had been imprisoned, as North Korea had found that Carter was an undercover CIA spy) and it was he who suggested to block his memories to ensure that he can't betray the North.
Amidst continuous chase and fight with North Korean coup, the Jung-Hee sends Carter, Ha-Na and Yoon-Hee ahead to intercept the train, while she and Dr Jung hold back the troops. Carter boards the train and manages to fight off the North Koreans trying to kill him and take Ha-Na back. General Kim had survived and led the North Korean attack on Carter. Yoon-Hee wakes up, apparently cured from the disease.Jung-Hee and Dr Jung catch up with the train on a truck. Carter kills Kim in his helicopter and joins Jung-Hee on the train with Dr Jung, Ha-Na and Yoon-Hee.As the train is crossing the bridge, the bridge explodes (presumably with the bomb planted by the CIA) making the train head for a fall.
