Set in the 1920's, during the Japanese occupation of South Korea, Lee Jung Chool was once a member of the Korean independence movement, but he now works as a police officer for Japan. He receives an order to take down the Korean independence group the Righteous Brotherhood.
Lee Jung Chool introduces himself to art dealer Kim Woo-Jin (Gong Yoo) and pretends to be interested in his Korean artworks. In actuality, Kim Woo-Jin is the regional leader of the Righteous Brotherhood. Both of these men are well aware of each other's true identities and intentions, but get closer to each other seeking out more information.
The Righteous Brotherhood learn there are spies within their group and attempt to clamp down on the moles. Soon, the identities of Righteous Brotherhood members are leaked and they flee to Shanghai, China. Meanwhile, Lee Jung-Chool and Japanese police officer Hashimoto (Um Tae-Goo) lead forces to Shanghai, China. There, members of the Righteous Brotherhood decide to acquire explosive for an attack on the Japanese government in Korea.
A mysterious virus suddenly spreads throughout Japan causing widespread panic. People infected with the virus are called ZQN. The ZQN attack people with superhuman strength and their victims also become ZQN. Hideo Suzuki happens to meet a female high school student, Hiromi Hayakari. They run away from the city together, but Hiromi has been already bitten by a baby ZQN. The baby ZQN that bit her did not have teeth and Hiromi is in half state of ZQN. They then meet Nurse Yabu at a shelter. Yabu hopes she can draw an antibody from Hiromi.
Based on the manga series "I Am a Hero" by Hanazawa Kengo.
