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.

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.

Si-mok selects key lawyers and police officers to be part of the special investigations team. Their probe begins with Dong-jae as the starting point.

Fearing for Ga-young's safety, Yeo-jin proceeds to transfer her to a different hospital. A nurse informs Yeo-jin of something strange that happened.

The truth behind Ga-young's convulsions is revealed. Chang-jun's wife receives a travel ban. Woo-gyun asks Chang-jun to help him get out of his mess.

Si-mok and Yeo-jin discover perplexing leads while searching Kyung-wan's basement. Dong-jae goes back to Chang-jun's office to fetch his cell phone.

Returning home from the rooftop party, Si-mok discovers that an intruder has left something in his bedroom. Yeo-jin and Geon come over right away.

Yeo-jin suspects a new killer is involved in the latest murder incident. Meanwhile, Si-mok collapses after leaving the autopsy.

Yeo-jin collects evidence as Si-mok interrogates the suspect. Many questions get answered, but the most important problem of all remains to be solved.

Si-mok sets out to meet the one he believes is the real murderer. He gets his hands on a bag that will determine the futures of many people.