On a sweltering summer day, sound effect engineer CHEN Jia-hui’s fiancé ZHONG Jia-hao suddenly disappears, leaving behind only a vague voice message. As the police investigate, the shocking truth about his use of multiple identities to commit emotional fraud is revealed. However, the matter was not over, and a year later, ZHONG Jia-hao’s body was found in the river under the identity of another person, CHEN Jian-kun, and the cause of death was unknown. During the police investigation, CHEN Jia-hui’s behavior and the hidden details in the voice file reversed the direction of the investigation. As the truth emerges, the voice becomes the key to unraveling the mystery – it not only records the truth of the past but also exposes the dark secrets of CHEN Jia-hui’s heart. A “perfect murder” of love and betrayal is quietly buried in the frequency of disappearing.