Set in the 1930s during Japan's colonial rule of Korea, many Korean resistance activists are based in Manchuria, northeastern China while hiding from Japanese authorities. In 1933, orders are given to assassinate Kawaguchi Mamoru, the governor of the Japanese garrison in Gyeongseong, and Kang In-gook, a pro-Japanese Korean business tycoon. For this covert mission, Yeom Seok-jin, an agent of the provisional Korean government who had broken out of prison in 1911, is tasked to do the same for three people and bring them to Shanghai: topnotch sniper Ahn Ok-yun, who's in a Manchurian jail for shooting her superior; Chu Sang-ok (nicknamed "Big Gun"), one of the last graduates of the Independence Military School and in prison after stealing guns from Chiang Kai-shek's army then selling them; and Chu's cellmate Hwang Deok-sam, an explosives specialist imprisoned for selling faulty product. The squad arrives in Gyeongseong, not knowing that one of them is secretly working for the Japanese and has hired freelance assassin Hawaii Pistol and his sidekick Old Man to kill members of the team.