Lee Dae-cheol is arrested for killing a few women and is sentenced to death 5 years later. Suddenly, a man claims to the police that he killed Lee's daughter, who had gone missing 3 days ago. Many issues in the case baffle the police.
The police secretly hunt for Lee Eun-hye, Lee Dae-cheol's daughter. The press gets the news and broadcasts it, causing embarrassment to the President. Genuine doubt is raised that Lee Dae-cheol is innocent and should not be hanged.
Park Gung-ho is released. He meets the stranger who had ordered him to kill Dae-cheol in jail, in exchange for his gambling debts. The stranger kills Park. Since Park had taken incriminating photos, Da-chang and Oh hunt for his mobile.
Pressure is put from many sides to ensure that Dae-cheol is executed, as decreed. Jo Seong-dae tries to kidnap Jin but is unsuccessful. Do-chang and Oh Ji reach Oh Jong-tae, Oh Ji's cousin, while following a lead about Dae-cheol's victim.
The private re-investigation into Yoon's murder continues. Jin interviews Nam Gun-hyeon, who is already against the re-investigation. Jin and Oh Ji analyze CCTV footage for Oh Jong's alibi, where Oh Ji finds the clue that it is doctored.
Dae-cheol signs the petition for his retrial. The judge is unsure so Jin tips off the media. A protest takes place and the petition is admitted. Do-chang has secretly decided to implicate himself. His superior and Captain Nam are worried.
Yoo, whose appointment as Minister is imminent, perceives Oh Jong a threat. Dae-cheol's retrial begins. Oh Ji's wrist-watch, bought in an auction, is a vital link in proving Dae-cheol's innocence. Several police officers are perturbed.
Captain Nam makes a key witness disappear. It seems that Yoon and detective Jang were killed by different people. Yoon Sang-mi gives false testimony. Do-chang's testimony is unfruitful. Dae-cheol's retrial is unsuccessful and he is hanged.
Do-chang's team has no work as punishment for the embarrassment caused to the department due to his hostile testimony. He and Oh Ji dig up dirt on Chief Moon. Oh Jong manages to get Oh Ji arrested for sexual exploitation of a minor girl.
Oh ji is exonerated. Chief Moon begs forgiveness from Eun-hye. Yoon is told to find a way to pressure Do-chang to stop his investigations. The case of Gung-ho's suicide is re-opened by the police. Seong-dae becomes the main suspect here.
Nam resigns from the police force. Police start a manhunt for Seong-dae. Oh Jong tries to get Seong-dae beaten to death at the docks, from where he was planning to flee the country. Do-chang arrest Seong-dae. Seong-dae implicates Oh Jong.
Oh Jong suddenly attacks Oh Ji with a knife. In the brawl, both are stabbed. The squad begins to go deeper in to the murder of Detective Jin-su. Jin increasingly suspects that her boss Yoo is somehow deeply involved in the whole matter.
Another past murder comes to light. Police find the remains of Jo Seong-gi. Sang-mi forces Chief Moon to resign. Jin assembles key links in the story. Oh Jong is arrested for inciting one of the murders. Mystery of Jung-seok's role grows.
The Justice Minister's former secretary is arrested. The head of the Civil Petition Division takes the fall for holding on to the related evidence. The squad does a search and seizure against Jung-seok. Jung-seok avers he killed somebody.
Jung-seok confesses in his newspaper that he killed Seong-gi and detective Jin-su. Jin writes definitively that Dae-cheol was innocent. Jung-seok tries to implicate Jong-dae so that he gets jail. Detective Nam has vital dash-cam footage.
Jung-seok jumps to his death, implying that Jong-tae pushed him. Jong is sentenced for life. Oh Ji finds the entire dash-cam footage which reveals that Nam killed Jin-su. Oh Ji shoots Nam to prevent him from stabbing Do-chang to death.
