Veteran detective Sang-gil and beat cop Eun-yeong are in charge of a case that seems to involve a simple act of self-immolation. Sang-gil initially thinks that it was an accident, but dog bite marks discovered on the body lead him to believe that someone had terrorized and murdered the victim. He and Eun-yeong investigate the source of the drugs found in the body and discover the victim had been pimping out young girls. At the same time, another murder involving a wolf-dog crossbreed occurs The two cases are labeled serial killings. With a connection between the victims uncovered, Sang-gil and Eun-yeong track down a potential witness. While questioning her, one of the mysterious dogs strikes out of the blue, killing the witness and stunning the cops.
- A series of mysterious murders to which the only clue is an animal bite mark There is a reason behind his killings. Sang-gil (SONG Kang-ho) is a homicide detective who is perpetually passed over for promotion. One typically dismissive day hes gets assigned yet another simple case, a suicide, as well as a rookie female detective, Eun-young (LEE Na-young), as a partner. Sang-gil grudgingly starts the investigation, but the case turns out to be a premeditated murder intricately designed to include a time-bomb. Blinded by the chance to earn a long overdue promotion, Sang-gil continues to investigate on his own without reporting to his superiors. Eunyoung questions the oddity of the bite mark on the body, but Sang-gil ignores her. Meanwhile, a seemingly random wild animal attack kills another person, and Eun-young senses a connection between the two deaths. Without realizing the seriousness of the situation, Sang-gil stubbornly continues to investigate the case alone, and Eun-young reluctantly follows along. When the two discover the bite marks on the bodies belong to a wolfdog, a cross between a dog and a wolf, they also discover that all the victims are connected to one another Why did a wolfdog go on a murder-spree?