In this small city by the river, night falls like water and mist fills the air. A young girl's murder case, unsolved for twenty years, has resurfaced. The city once seemed peaceful, but this new case awakens people's memories and stirs up trouble once more.
Jun Mo was once an ignorant boy from this small city. Now he has grown up to become a police officer. When he returns, he finds that the painful memories of the past remain vivid. The unsolved murder of the girl is a wound in his heart that cannot be erased. He decides to pursue the killer again and uncover the truth.
As the investigation deepens, Jun Mo discovers that everyone involved in the case back then has undergone earth-shattering changes because of this mystery from twenty years ago.
At night, mist swirls along the riverbank. Jun Mo walks the path of pursuit, repeatedly confronting questions of human nature. The friendships, family bonds, and love of the past all seem so fragile in the face of this case. Yet he believes that the truth will eventually come to light.
During the investigation, Jun Mo encounters one unexpected crisis after another. Each crisis brings him one step closer to the truth. He uncovers many secrets about the people involved in the case back then: their past, their present, and their future.
