Eccentric investigator Xing Kai (Owen Cheung) and police superintendent Ding Luofeng ( Lam Bo-yee ), despite sharing remarkably similar backgrounds, have taken different paths in life. A series of serial murders brings the two together. Xing Kai and Ding Luofeng develop a mutual admiration and join forces to apprehend the killer. During the investigation, Xing Kai is forced to seek help from an old adversary—psychologist Yang Zhifei (Kelly Fu)—to aid in capturing the perpetrator. As the trio delves deeper, they discover the killer is not a single individual but an entire assassination organization. The killers use the framework of the "New Seven Deadly Sins" promoted by a mysterious website to execute each victim who has committed one of these new sins, targeting every member of society. The three must race against time to capture them before more victims appear.