In the city of Muyoung, the body of a young woman in her twenties is found near a greenhouse complex. The perpetrator leaves a gruesome signature by slashing the corners of her lips. Detective Ryu Sung-Joon, driven by rage, becomes relentless in his pursuit and captures the suspect. Despite overwhelming evidence pointing to him, the suspect claims his innocence and demands a jury trial.

With overwhelming evidence against him, Jung Man-Chun is identified as the killer. The nine jurors unanimously find him guilty, and Judge Ryu Sung-Hoon sentences him to life imprisonment. That evening, the jurors gather for a dinner at Charles's restaurant.

During a tense standoff, Ryu Sung-Joon and Jung Man-Chun are injured and hospitalized. While they are recovering, another woman's body is discovered in a park, bearing the same gruesome signature as the first murder. Is there a copycat on the loose, or did the real killer remain at large?

Baek Moon-Gang seeks revenge on Jung Man-Chun for his daughter's death and confronts him in the hospital. Feeling threatened, Jung Man-Chun reveals a shocking truth: a person named "Yoon-jae" orchestrated everything. Moon-Gang recalls a boy with number 13 from the "Hope Welfare Center" and begins to suspect that Ryu Sung-Joon might be that boy.

Framed for the murder of Jung Man-Chun's family, Ryu Sung-Joon is on the run. Jo Eun-Ki is the only one willing to help, hiding him in a warehouse at her children's center. She seeks help from Ryu Sung-Hoon, who agrees to meet Sung-Joon.

The brothers secretly collaborate to catch the real killer, "Yoon-jae," and clear Sung-Hoon's name. As they track the killer, a child from Jo Eun-Ki's center, Yuna, is brutally attacked. Sung-Joon identifies the suspect, Choi Soon-Gil, from Yuna's drawing of a tattoo and confronts him, finally uncovering a crucial piece of the puzzle.