The story takes place in the fictional modern city "Fog City", a city shrouded in thick fog all year round, just like its dark humanity. Police detective Xia Yubing and forensic doctor Shen Ze formed a partnership to solve bizarre cases. As the investigation deepened, they gradually discovered that these cases were not isolated, but related to a huge conspiracy. In the process of pursuing the truth, Xia Yubing not only had to face the cunningness of the murderer, but also faced obstacles from power, money and humanity. She and reporter Zhou Yun used each other and helped each other to jointly expose the darkness hidden deep in the city. The story runs in parallel through multiple clues, showing the various social aspects of the foggy city and the complexity of human nature. In the end, Xia Yubing overcame numerous difficulties, brought the criminals to justice, and completed his own redemption.
