Season 1

On the 30th of June, 1997, a mysterious father-and-daughter duo arrived at Yuanlongli. They take the elevator to the abandoned 18th floor. When the security guards arrive, they find only the strange traces left behind by the two of them.

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

He Yuan Hang 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 Yuan Hang 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 Yuan Hang and Ran Fangxu beat around the bush to make Wu Shanlong expose himself. Both of them deduce that Song Qing Song ordered Wu Shanlong to hire a hitman to get rid of Xu Meng.