Two years after the events surrounding Chang-joon, Si-mok is now a Prosecutor at the Tongyeong Prosecutors Office, waiting to be transferred to the Wonju Prosecutors Office. On his way through a seaside road on a foggy night, he is disturbed by a removed portion of a restricted fence at a beach nearby. Upon turning back, he discovers that emergency services has found two drowned bodies. He speculates that the incident, initially thought of as an accident caused by the victims, may have been instigated by another party. Yeo-jin, now a Senior Inspector at the Korean National Police headquarters, calls Si-mok and provides information about a couple who might have been involved in the incident at the time, before being assigned to a reformation unit by her Chief Choi Bit (Jeon Hye-jin), who is frequently incensed by the ostracism the Prosecution depicts the Police to the public. Despite finding promising leads, Si-mok is surprised to find out the case is immediately closed as a non-suspicious deposition at the Seoul Prosecutors Office.

Si-mok continues to investigate on the drowning case and lodges a complaint to have it reopened. Yeo-jin, who meets with Choi Bit after an internal investigation is formally charged at their Police Superintendent, and finds out that the Prosecution has been targeting their Superintendent in a power struggle for investigative authority. Choi Bit meets with one of the victims' father and publicly implies the wrongdoing of the Prosecution in immediately closing the case. Si-mok is summoned by Chief Woo Tae-ha (Choi Moo-sung) at the Supreme Prosecutors' Office to join a Prosecutor-Police Council, and later inquires with his former Chief Kang Won-chul of the Seoul Prosecutors' Office about a Special Treatment in the drowning case. Yeon-jae, Chang-joon's widow and now CEO of the Hanjo Group, is infuriated upon discovering articles portraying her as complicit in using her husband to take over her family's business. Dong-jae, now a prosecutor at Uijeongbu Prosecutors' Office, presents Choi Bit's incriminating history to Tae-ha. Both Si-mok and Yeo-jin are summoned by their respective Chiefs to prepare to defend their agencies' interests in the forthcoming council.

Yeo-jin tries to recruit Jang-geon, now a lieutenant, to the Council. Si-mok is assigned to investigate on the case Dong-jae has submitted to Tae-ha, which involves a suicide of a sergeant at the Segok Police Station. Yeon-jae hires a former district judge-turned-lawyer to become her internal counsel to persuade Won-chul in comdenming The Sungmoon Daily article.

The police-prosecution council convenes for the first time, but was adjourned early after the debate of both sides has reached an impasse. Dong-jae schedules a meeting with Yeon-jae, whose chairmanship of her company is on the risk of losing to her stepbrother. He brings up a case involving the mysterious death of a former prosecutor, which leaves her concerned. After Choi Bit catches wind of Dong-jae investigating the Segok incident, she sends Yeo-jin to intercept his probe.

Yeo-jin informs Choi Bit that the Segok incident may have also been a homicide, causing Choi Bit to be alarmed at its potential to be incriminating to the police's objective. Si-mok requests Won-chul for a warrant, but faces a problem instead. On her way to Anyang Correctional Facility to interview a suspect on the Segok case, Yeo-jin is surprised to see someone familiar who is also incarcerated there. Choi Bit later directs her to retrieve a sealed document and deliver it to an Assemblyman who is about to file a threatening lawsuit to the police, leaving a frustrated Tae-ha to order Si-mok to find its contents.

Yeo-jin secretly makes a copy of the sealed document despite Choi Bit's orders not to open it, but Si-mok finds its contents himself nonetheless. Yeon-jae attempts to persuade the editor of The Sungmoon Daily, who owns a detrimental stake at her company, to join her side.

Dong-jae is found to be missing, causing both the prosecution and police to conduct their own search. As Si-mok retraces Dong-jae's whereabouts and his current cases, a worried Choi Bit directs Yeo-jin to look for evidence of the police having no involvement in his disappearance.

As the search for Dong-jae continues, Choi Bit is concerned he was probing about her the day he went missing and arranges for a clandestine meeting with Tae-ha. Si-mok receives a list of Dong-jae's upcoming indictments, and starts his inquisition with Yeon-jae at the Hanjo Group. Meanwhile, Yeo-jin interviews the convicts from the Segok case and how it may be connected to Dong-jae's. As Dong-jae's wife makes a public appeal on television, news broke out that a police officer may have been involved in his kidnapping.

A culprit sends a message about Dong-jae to the public, which leaves the police to be openly ostracized. Si-mok and Yeo-jin analyze its contents. After receiving news of Choi Bit's involvement about the former prosecutor, Yeon-jae suspects Woo-chul and the Western Seoul Prosecution are about to file charges against her company, but changes her focus to Choi Bit and her connection to the former prosecutor's death, whose articles were also incidentally the last websites Dong-jae had visited prior to his disappearance.

Si-mok becomes frustrated when Dong-jae's team openly divulges information on the cases he has left behind. While Yeo-jin investigates a potential lead involving the police, Si-mok investigates the former prosecutor. His progress on the search is noticed by Choi Bit and Tae-ha, who both want him to look for another lead instead. An eyewitness who claims to know about Dong-jae's abduction leaves a comment on the internet, wanting to come forward.

The Segok officers are summoned to explain themselves to the police, with one of them being identified by an eyewitness as Dong-jae's abductor. However, Si-mok and Yeo-jin are concerned about the witness's testimony, and both try to recreate the crime scene based on his account. Tae-ha convenes the press to condemn the police and wants the prosecution to take over the investigation, leaving the police in a precarious position.

Tae-ha and Choi Bit meet privately and discuss about the former prosecutor. While Tae-ha raises worriment about the former prosecutor's wife, Choi Bit is concerned about the judge-turned-lawyer and his persistent inquiry about the case. This causes an alarm to Yeon-jae, who arranges for a meeting with both of them. At the second police-prosecution council, Si-mok's hearing disorder returns to plague him.

Despite Tae-ha's orders for him not to prowl around, Si-mok continues to investigate the former prosecutor's death, beginning with him inquiring with Won-chul about it. A member of Dong-jae's team later gives Si-mok an information about a student assault case Dong-jae has recently taken. After discussing with Yeo-jin about it, they find out its connection with the Tongyeong drowning incident.

Si-mok and Yeo-jin chase after a suspect from the Tongyeong drowning incident and his connection to Dong-jae. A search party is formed to look for the missing prosecutor, while the fake eyewitness is summoned by the police.

Tae-ha meets with Yeon-jae about the Hanjo trial and the former prosecutor, whose mystery surrounding his death continues to be probed by Si-mok. Si-mok confronts Tae-ha about it, only to be threatened by the latter. Joined by Yeo-jin, they found out more people are involved in it, including Choi Bit.

Despite Tae-ha's threats to Si-mok and Yeo-jin, both prosecutor and police officer file formal investigation warrants in their respective agencies, resulting to Choi Bit public resignation and Tae-ha being put into trial. Won-chul also resigns and hands over the Hanjo case to the Central Seoul Prosecutors Office, forcing Yeon-jae to choose between keeping her company or continuing her late husband's legacy. She later visits an unconscious Dong-jae at the hospital. After recovering, Dong-jae reports to work and is interviewed about Hanjo's involvement with the former prosecutor. With their units now disbanded, Yeo-jin is transferred to the National Police's Intelligence division, while Si-mok is sent to the Wonju Prosecutors Office.