Police detective A-Hao investigates a mysterious stabbing by a teenage girl who appears to be possessed by a malevolent force.  Once a passionate detective, A-Hao retreated from the front lines several years ago after mishandling the investigation of a wife killer. By chance, he stumbles onto a mysterious stabbing allegedly committed by a teenage girl, which drags him back into the investigations unit.  Initially, A-Hao just wanted to quickly close the case, but his investigation into mysterious suspect Wang Jia-ying gradually ignites his desire for the truth.  As A-Hao edges closer to cracking the case, Wang Jia-ying begins exhibiting signs of demonic possession. Despite opposition from everyone around him, A-Hao insists on exhausting all possibilities to uncover the truth, not realizing he has already fallen into a trap weaved by lies and conspiracy…