Ray Owens is sheriff of the quiet US border town of Sommerton Junction after leaving the LAPD following a bungled operation. Following his escape from the FBI, a notorious drug baron, his gang, and a hostage are heading toward Sommerton Junction where the police are preparing to make a last stand to intercept them before they cross the border. Owens is reluctant to become involved but ultimately joins in with the law enforcement efforts
Kyung-chul (Choi Min-sik) is a dangerous psychopath who kills for pleasure. He has committed infernal serial murders in diabolic ways that one cannot even imagine and his victims range from young women to even children. The police have chased him for a long time, but were unable to catch him. One day, Joo-yeon, daughter of a retired police chief becomes his prey and is found dead in a horrific state. Her fiance Soo-hyun (Lee Byung-hun), a top secret agent, decides to track down the murderer himself. He promises himself that he will do everything in his power to take bloody vengeance against the killer, even if it means that he must become a monster himself to get this monstrous and inhumane killer.
Doomsday Book is an anthology movie, split into 3 different chapters. The first Chapter, entitled Heaven’s Creation, is about a robot who comes alive and follows what happens afterward. The second Chapter, entitled The New Generation, is a story from the point of view of a boy who is now a zombie. The third Chapter, entitled Happy Birthday, re-interprets “The Christmas Gift” by O Henry.