Su Wan, a lecturer in criminal psychology, was rescued by her fiancé Gu Huai as a survivor in the "Phone Devil" serial murder case three years ago. When life gradually calmed down, a number that was supposed to disappear with the death of the murderer rang again, breaking all illusions.
Su Wan started investigating, but encountered Gu Huai's almost paranoid obstruction and house arrest. She formed an alliance with the newly transferred criminal psychology consultant Shen Tinglan, and followed the clues of the "water drop sound" and strange symbols to locate the abandoned electroplating factory, but the police were alerted and the operation was blocked. During the investigation, Su Wan discovered that the key evidence secretly hidden by Gu Huai pointed to a cult organization called "Tingtong Society" and its victim "Lin Xiaoman".
Gu Huai confessed during the conflict that Lin Xiaoman was his unrelated sister who was selected as a "sacrifice" by the Listener Association many years ago and disappeared. The huge trauma distorted his desire to protect. At this time, the mysterious masked man continued to provoke, using voiceprint technology and psychological tactics to mark Su Wan as a new target.
In order to break the situation, Su Wan took the initiative as bait to lure the masked man to appear in the abandoned broadcast tower. In the final showdown, Su Wan relied on psychological profiling to reveal her true identity - Han Jing, Lin Xiaoman's best friend, seeking revenge due to twisted admiration and hatred. The crisis is over and the truth is revealed at dawn.
Su Wan finally broke free from the shackles of trauma and emotion and moved towards self-rebirth, while Gu Huai also gained the possibility of reflection and redemption in the ruins.
