In the spring of 1940, Japan occupied Tianjin. Shen Yan, an accountant in a medicinal materials store who appears to be obedient, is actually a CCP agent code-named "Dark Blade". When his only contact "Lao Zhou" suddenly disappeared and Japanese plainclothes appeared at the meeting point, he realized that the sleeper team had been infiltrated. In order to obtain top-secret information about the Japanese and puppet "Haiguang Project", Shen Yan must use the most primitive methods - observation, memory and judgment in the desperate situation of losing contact with the organization and being hunted by the "shadow", to complete a silent hunt alone in the streets, docks, dance halls and drug stores of Tianjin Wei.
