In the former state-owned Xuri Factory, a woman with amputated feet is accidentally discovered in an abandoned sewage pool. The deceased is Shen Xiaozhou, the daughter of an employee. Lian Haiping, a middle-aged detective who is outwardly depressed but warm on the inside, and Shi Qiangfeng, an impetuous and hot-blooded rookie cop, unexpectedly become partners. Although they have gripes with each other, they must work together to find the real culprit. As they investigate one suspect after another, the two discover that behind the seemingly morally upright college student victim, there are many unexpected social aspects. Meanwhile, an old case that is deeply intertwined with the two people gradually surfaces. The relationship between Lian Haiping and Shi Qiangfeng becomes complicated because of "an old case" and "a past event." While the investigations are ongoing, cases of female households with amputated feet occur one after another, casting a shadow over the Xuri Factory that was once full of life. Lian Haiping also discovers that there is a force deliberately guiding the direction of the police investigation. As the fog seems to be clearing up, the undertow is already surging.