A drug cartel boss is arrested in a raid and coerced into betraying his former accomplices as part of an undercover operation.

Su Cheng returns to his hometown after several years abroad to find his best friend Wang and old crush Lin Jing married and settled down. Cheng's memories of the city reflect a difficult childhood suffering from depression and frequent fights with classmates. Suddenly Wang is found brutally murdered in what police suspect to be one of a series of serial killings over cheating spouses. The killer kidnaps the cheating couple and tortures them before murdering one and leaving the other as a witness. Jing refuses to believe her husband would have cheated on her and desperately searches for answers to his death. At her side, Su Cheng seeks to protect Lin Jing while keeping his own dark secrets at bay. Meanwhile, police suspect Su Cheng may have had something to do with the crimes. Is his return really as coincidental as it seems?