Light to the Night

Ran Fangxu insists on investigating the route of the disappearance on the 18th floor, while He Yuanhang believes that directly searching for the missing people would be more efficient. The disagreement escalates, and the two go their separate ways.

He Yuanhang receives a message that someone wants to provide information about the missing father and daughter in person. The informant, Su Yuzhi, says the missing girl is her coworker, Xu Meng.

Ran Fangxu discovers the relatives of the Xu family. He decides to split up with He Yuanhang to visit them separately.

A theft occurs at the mine, and the precinct is setting up a task force. Ran Fangxu is also assigned to it. However, Ran Fangxu insists on continuing the investigation into the yet-to-be-filed missing persons case of Xu Meng and her father, and even assesses that it may be a homicide.

Wu Shanlong arrives at Nanshan police station. He Yuanhang and Ran Fangxu beat around the bush to make Wu Shanlong expose himself. Both of them deduce that Song Qingsong ordered Wu Shanlong to hire a hitman to get rid of Xu Meng.

Ran Fangxu and He Xiaohe run into the property manager, Qian Dajun, in the underground parking garage. Qian Dajun claims he is fixing the wiring and carries away an electrician's tool bag. Ran Fangxu uses the Tremaux algorithm to sweep the building and brings He Xiaohe up to the rooftop, where they run into Qian Dajun again.

He Yuanghang and Ran Fangxu found Su Yuzhi. She tells them that Boss Sun's name is Sun Zhengyong, who once tried to keep Xu Meng as his mistress. He Yuanhang and Ran Fangxu split up to find clues about Sun Zhengyong.

After opening the elevator doors, they see handprints and footprints left inside the lift, along with Xu Meng's handwritten note. They speculate how the father and daughter escaped from the elevator. He Yuanhang and Ran Fangxu return to the police team, where Captain Feng gives them high praise.

Ran Fangxu visits He Yuanhang's home to have a meal. He is warmly welcomed He Yuanhang asks Ran Fangxu to help him hide the fact that he's returning to the station.

He Xiaohe takes He Yuanhang to a psychiatric clinic. The doctor recommends long-term psychological counselling, but He Yuanhang dismisses the doctor as a fraud and refuses to undergo treatment.