Chi Kook has been found at the prison with multiple stab marks all over his body along with a message written in blood. Not long after that, Chi Kook’s watch, a present gifted by Ba Reum and Dong Koo, was retrieved at the grape farm murder site, leading Ba Reum to join Moo Chi for the investigation. Meanwhile, Bong Yi’s grandmother stumbles upon something she should’ve never found out while working as a cleaning lady for Bong Yi’s settlement money.

Chi Kook’s sudden death shocks everyone and Ba Reum tries to convince Chi Kook’s mom in requesting an autopsy. Meanwhile, Detective Ko starts to doubt that Sung Yo Han was the real killer. He starts to dig deeper into Song Soo Ho’s past.

Ba Reum finally remembers what exactly happened to his family. He tries to set a trap to catch the mysterious OZ, and he finds out a secret about Dr. Daniel Lee in the process. Meanwhile, Moo Chi finds the unregistered car the OZ, the murderer who killed Chi Kook, used.

Moo Chi finds out that Ba Reum was the killer and ferociously charges after him at the station. Moo Chi also suspects Detective Lee being part of the OZ organization and tries to carry out an investigation on the two, but it’s not easy. As flustered as he is, Ba Reum tries to remain calm to buy time until he figures out the killer of Chi Kook.

Moo Chi and Bong Yi get closer to the truth. In the meantime, Ba Reum tries to find his aunt, the last missing puzzle piece. Sang, who tries to confirm Ba Reum’s alibi, finds something suspicious at Ba Reum’s house.

Ba Reum makes the final decision to turn himself in and finish one last mission that only he can do. Hong Ju also shares her big secret that’s been tormenting her for years on her last show with Hee Jin, a woman who in fact was a secret agent working for Choi Young Shin under a massive private organization.