Song Zhi, a new addition to the Fuhaishi Criminal Investigation Unit, becomes a pupil of Captain Guo Yong. Together, they solve a case involving a set of human remains. The victim is Xia Qian, a university student who disappeared six years ago. Wan Hong, the policewoman who investigated her disappearance back then, now lies unconscious in a hospital bed.
The disappearance case from six years ago was baffling. One by one, all kinds of suspects came to light, each with tangled connections to Xia Qian. Everyone had a motive and bore her ill will, but there was no direct evidence. The investigation was fraught with difficulties, and the case became a cold one.
With the discovery of the remains, the missing-person case becomes a murder investigation. Guo Yong and his pupil Song Zhi team up to reopen it. They visit the former suspects one by one, pore over the old case files, and read the diary Wan Hong left behind, hoping to find the slightest clue to the truth. They move between two different points in time.
The two investigators focus on tracking down the real killer, not only to clear Xia Qian's name, but also to fulfill the wish Wan Hong has carried in her heart for years. Yet as the truth draws closer, everyone connected to the disappearance is caught in a labyrinthine whirlpool...