As a teen, prosecutor Hwang Si-mok received surgical treatment for his abnormally developed brain, but the procedure left behind serious side effects.

The convict's strong plea for his innocence prompts Si-mok to review the CCTV clip. At the Yongsan police station, he runs into officer Han Yeo-jin.

Si-mok volunteers to appear on live national TV to discuss Kang Jin-seob. He also makes a bold promise to find the culprit within two months.

Rumors quickly spread about Si-mok's violent nature. Regardless, he persists in his investigation. He finds his mentee, Young Eun-su, suspicious.

Si-mok, puzzled by the details of the most recent murder case, visits the victim's home to seek more clues. Yeo-jin joins him in the investigation.

New pieces of evidence only increase the list of possible suspects. In the midst of the confusion, a few begin to question Si-mok's innocence.

Si-mok and Yeo-jin team up to covertly pursue Seo Dong-jae. Just as Dong-jae is about to throw something into the Han River, Yeo-jin stops him.

Enraged by what the police did to Park Kyung-wan, Yeo-jin tries to confront her superior but is stopped by Si-mok, who warns her of the consequences.