Episode Summary
Former detective Xu Jingzhi is now a professor, but his past comes back to haunt him when a stalker, Zhuang Mingcheng, murders an old acquaintance connected to Xu's childhood trafficking trauma. Zhuang kills the man as a twisted "gift" to Xu. Xu joins the investigation and notices clues linking the murder to a book Zhuang gave him. Flashbacks reveal Xu escaped a trafficking ring as a child but left a younger boy behind, who is implied to be the killer, Zhuang.
Spoiler Alert
The Professor with a Past
We start with Xu Jingzhi. He used to be a top-tier detective. Now, he is a criminal psychology professor at Wuyang Police Academy. He left the force because of a past case that messed him up. He calls it his "inner demons."
He goes to work like it's a normal day. He doesn't notice someone is stalking him and taking photos. In class, he lectures on the criminal mind. A student asks the big question. Why did he quit the force to teach? Xu stays silent. He doesn't owe them an explanation.
Zhuang Mingcheng is sitting in that class. He watches Xu closely. After class, an old man named Lu Youliang shows up looking for the professor. Zhuang intercepts him. He lies and says Xu doesn't teach there anymore. He offers to help Lu contact him instead. Lu falls for it and hands over Xu's number.
A Brutal "Reunion"
Zhuang slides a note under Xu's door later. But his real business is with the old man. He tricks Lu Youliang into meeting at a boat by the sea that night. He claims Xu will be there.
Lu walks into the dark boat. It’s empty. Zhuang steps out from the shadows with a dagger. He doesn't hesitate. He attacks. Lu is confused and terrified. He asks why. Zhuang says he is taking revenge for Xu Jingzhi.
Lu panics. He assumes Xu hired a hitman to settle a score. He starts blabbing. He confesses about a man named Jiang Yongquan. He claims he raised Xu and shouldn't die like this. Zhuang doesn't care. He cuts Lu open and watches him bleed.
The Phone Call
This part gets twisted. Xu Jingzhi calls Lu's phone. Lu is lying on the floor, dying. Zhuang answers the phone but doesn't speak. He holds it up to Lu's ear. Then he pulls it back. He just listens to Xu's voice on the other end. He enjoys it. It’s clearly a sick obsession.
We get a glimpse into the past. Xu wasn't always Xu. He was trafficked as a child and named Lu Yuan. He had a little "brother" in that hellhole named Lu Ran. Lu Ran had a mentally unstable mother. Xu wanted to escape every day. Eventually, he did.
The Wax Corpse
A fisherman finds Lu's body the next day. Detectives He Ya and Liu Ming arrive at the scene. It’s a weird one. The killer dragged the body and sealed it in beeswax. The cuts on the body are unique.
Xu gets the call. His superiors order him back to the bureau to help. He hits the library to research the victim's clothes. He needs to get inside the killer's head.
Zhuang has his own workspace. It’s a creepy basement covered in photos of Xu. He finds Xu at the library. He plays the fanboy. He says he likes Xu's work. Xu gives him the cold shoulder. Zhuang leaves a book behind.
Old Ghosts
Xu goes home and keeps digging. He realizes something strange. The cuts on the dead body match a pattern from the book Zhuang left. It’s a specific signature.
He looks at his old awards. He remembers a warning from his boss. The trafficking ring that kidnapped him is active again. They have been hiding in the shadows for years.
Xu thinks back to his escape. He didn't just run away. He had to leave his little brother, Lu Ran, behind. He caused a pursuer to die in a car crash during the getaway. He told the police he left the boy there.
Back in the dark room, Zhuang stares at a photo of Xu. He smiles. He whispers that he is finally back. The little brother has returned.
