Season 1

Do-han has his suspension lifted and gets called to a murder crime scene by Jong-hun. As he arrives at the scene, he encounters the dead body of Song Young-jin, the accomplice to the biggest fraud case of the century, the No Sang-cheon Ponzi scheme case. He also finds traces of No Sang-cheon who had died eight years ago.

As he keeps watch on the suspect Byeong-jun, Do-han suspects that the case is connected with No Sang-cheon's fraud victims' organization. Then comes the second murder, in which the victim reports to the police that No Sang-cheon is trying to kill him. At the scene of the second murder case, Do-han runs into Byeong-jun yet again and reinvestigates the case as a serial murder.

As Do-han tries to release Byeong-jun having no clear evidence, Byeong-jun suddenly confesses to the murders. Meanwhile, Na-yeon prepares for a press release about the serial murder cases, and Jong-hun hears surprising news from Byeong-jun when he visits him at the Prosecutor's Office.

Jong-hun looks into the past BIGS Network investigation files and finds out that the unreleased first murder victim was So-ram. Meanwhile, Na-yeon is prevented from releasing any articles regarding the case, so she reveals to Do-han that the murder victims are dying in the order on Jae-hwang's list.

Jong-hun, tormented by the impending doom that is written on the list, disappears. Do-han manages to find where the new suspect Jae-hwang had been staying after his release, but encounters Jae-hwang in an unexpected situation.

Jong-hun says that he was abducted by Jae-hwang, and the case seems to come to a close with suspect Jae-hwang's death. However, as Na-yeon and the victims' group receive another murder message, everything falls into chaos.

After learning of Da-jeong's investment briefing, Do-han makes a visit and witnesses a shocking scene. Meanwhile, Jong-hun vows not to cover up anything any longer and starts to delve into the case. In doing so, he tells Do-han the truth about the night of his abduction.

Determined not to repeat his mistakes, Jong-hun looks back at his shameful past and reinvestigates the No Sang-cheon fraud case. In the process, he unexpectedly runs into the ones that helped No Sang-cheon flee previously.