The Sin of Purification

On a stormy night, a woman's body is found in a locked bathroom. The bathtub water is an eerie pale blue, and a mysterious symbol, "♰," is carved into the mirror. Detective Captain Chen Mo discovers that the case is connected to a mass death at a psychiatric hospital twenty years ago. His father, a veteran detective who handled that case, suddenly "died in an accident" soon afterward. When a second victim appears, drowned in a bathtub and marked with the same symbol, Chen Mo is forced to confront his family's secrets: his father may have been involved in illegal drug experiments, and the killer is following some kind of "purification ritual," hunting down the descendants of those involved one by one. More frightening still, the real culprit seems connected to "the Judge," a serial killer executed three years ago, and may even be an experimental survivor who was supposed to be dead. As the investigation deepens, Chen Mo discovers that his blood contains the only antibodies capable of countering the mind-control drug "TS-117." The killer wants more than revenge. With a "seawater purification" operation covering the entire city, they intend to complete the deranged experiment interrupted twenty years ago...