Lin Mo, an ancient book restorer, suddenly awakened to a strange ability - he could "see" the strong negative emotions of others, and those anger, sadness, and fear condensed into concrete black in his eyes. When he discovers mysterious purple traces in an old book and becomes involved in a disappearance of a female college student ten years ago, he gradually realizes that he is not the only "emotionally gifted person", but that there is a century-old monster hidden deep in the city that makes a living by devouring other people's emotions.
As the investigation deepened, Lin Mo met a mysterious neighbor who could hide his emotions, the victim's mother who was twisted by obsession, and "similar people" who also had supernatural powers. They form a fragile alliance, but discover that there is an ulterior secret hidden in everyone's heart. As the truth was peeled back layer by layer, the boundary between the perpetrator and the victim began to blur, and the murderer Lin Mo saw in the mirror looked more and more like himself.
This is a story about "seeing" and "being seen". In the abyss of emotions, no one is pure light, and no one is completely dark. When the final showdown comes, Lin Mo must make a choice: use his ability to judge others, or learn to coexist with the blackness in his heart? And that invisible line that connects everyone may be the only way through the darkness.
