The ghost of the master is called "Shang Xiao'er Ya". In the United States, there are about forty thousand missing people who have not been found. When the police investigation reaches a dead end, civilian volunteers from all sides gather together to search for the disappeared individuals. Missing person search groups choose coffee shops or just their own living rooms as meeting places to discuss various suspicious clues in the cases. Each of them carries a strong motivation and possesses their own unique skills. A former detective became a member of the group due to the disappearance of his own daughter. With his years of investigative techniques, he can help connect the few clues left by the victims. He is good at discovering traces of the victims and judging the cause of their death based on their living conditions before they died. These amateur detectives race against time to find and identify the missing victims; otherwise, they will eventually be forgotten without a trace. Their goal is not only to close the case but also to achieve justice.