The 1920s, when Korea has fallen under Japanese rule.
Lee Jung-chool (SONG Kang-ho), a Korean police captain in the Japanese police force, is given a special mission to infiltrate the armed resistance fighting for Korean independence. He approaches Kim Woo-jin (GONG Yoo), a leader of the resistance. These two men, standing on opposite sides of history, each knowing the identity and intentions of the other, form a close bond without revealing their inner thoughts.
Meanwhile intel is being leaked on both sides, and no one knows who the informants are. Members of the resistance meet in Shanghai to obtain explosives that will be used to destroy facilities of the Japanese Headquarters in Seoul, while the Japanese police follow them and gather in Shanghai. The pursued and the pursuers, locked in an operation where each side uses the other, are thrown into a confusion of secret enmity and conciliation.
Meanwhile, a train carrying explosives passes the border and heads towards Seoul...
