A serial killer is on the loose. As Do-chang battles past trauma, the investigation grows murkier, only taking him further from the truth.

Do-chang’s guilt grows after another unexpected death takes place. Others want to wrap up the case, but Do-chang and Ji-hyeok refuse to give up.

The detectives find some strong evidence and start going over CCTV footage. A man burns mysterious objects, and makes a suspicious approach.

Do-chang and Ji-hyeok are hot on the killer’s heels, but elsewhere another murder is underway. Cheon Sang-u keeps an eye on Cheon Na-na.

Do-chang finds out about the killer’s tragic past and realizes that one piece of his pattern of murders doesn’t line up. He induces a confession.

Na-na follows Sang-u and finds some evidence. The team is threatened with being broken up. The detectives investigate Jung Hui-ju’s acquaintances.

Kim Min-ji’s background is revealed. The detectives get proof that incriminates TJ Group executives. Ji-hyeok is curious about Na-na’s intentions.

Na-na’s press conference throws Woo Tae-ho into disarray. A suspect in the Hui-ju case is caught and some clarity is brought to the case.

The detectives question Na-na about the car accident. They investigate Tae-ho's previous whereabouts, but Choi Yong-geun is looking into this too.

Na-na preys on Sang-u’s weaknesses. A mysterious man follows Moon Bo-kyeong, while Yong-geun plans to use her connections to his advantage.

Yong-geun is arrested, but uses his experience to make the interrogation difficult. The detectives search for a motive for Sang-u’s murder.

Sang-u is furious after realizing that Na-na came close to turning him in. Ji-hyeok provokes Yong-geun in an attempt to make Sang-u culpable.

The detectives ask to reopen Tae-ho’s case and look for further evidence regarding his death. Na-na asks Ji-hyeok to make an allegiance with her.

The detectives question the gang who tried to kill Hui-ju’s grandfather. As they get closer to the truth, Na-na and Jang Ki-jin get into trouble.

Na-na passes evidence of her father threatening her to Ji-hyeok, but he uses it against her. Ki-jin files a false charge against Do-chang’s team.

While the detectives search for proof of Na-na’s crimes, she becomes chairman of TJ Group. Ji-hyeok gives testimony to get Sang-u released.