The serial killer "Morning Bird" specializes in committing crimes on rainy nights, but he sends "Good morning" to Su Mian, the leader of the serious crime team, every morning. After three years of chasing the murderer to no avail, Su Mian was forced to cooperate with criminal psychology consultant Wen Renjue, only to find that her every step was predicted by the murderer. When forensic doctor Shen Tang discovers shrapnel from an old case from twenty years ago buried in the body of the deceased, and archivist Lao Zhou loses his memory inexplicably, Su Mian begins to suspect that the murderer is around. The secret behind Wen Renjue's gentle mask and Chen Mo's action information leaked due to being blackmailed made this cat-and-mouse game even more confusing. The good morning text messages continued, but Su Mian couldn't tell whether it was a warning or another confession.
