Episode 10 begins with Tae-heon getting dismissed because he didn’t report the photographs of Jung-won. Thanks to the video of Jung-won sitting by Eun-sae’s corpse, the police search her house and she gets arrested. Yoon-young, on the other hand, is released. Reporters, including No Ji-ho, crowd Jung-won as she’s taken to the station. Meanwhile, Woo-jae begs his father to get Jung-won out but he believes public opinion is too strong. Only catching the real culprit will help.
Yoon-young meets Woo-jae and the latter promises to prove she and Soo-rin committed the crime. When Yoon-young isn’t deterred, Woo-jae gets on his knees and asks her for help. They can blame Soo-rin and get Jung-won out. In return, Yoon-young asks if he will marry her.
Elsewhere, Assembly man Mo Mo reconsiders his partnership with Seol Pan-ho since his daughter-in-law is now a murderer. Yoon-young meets Soo-rin, who is set to leave the country the next day. She gifts her a clock. Soo-rin is grateful, not just for the gift but for Yoon-young helping her “get out of that terrible house”. Then Yoon-young tells Soo-rin to hide the knife in the memorial hall where Jung-won’s father’s ashes are kept so that she will be convicted. Soo-rin genuinely seems to want to help and agrees.
As expected, Myung-soo meets Tae-heon and tells him that Soo-rin is leaving the country soon. They get a phone call and Tae-heon finds himself being investigated by the police’s internal department. He then gets a text from Seol Woo-jae. Tae-heon asks to use the loo and escapes from the building. Meanwhile, we see Woo-jae looking at a divorce form and a marriage registration form. He goes home to find Yoon-young lounging in the bathtub. When she’s out, he shows her the forms as proof. At one point, she takes Woo-jae’s phone and secretly installs a wiretap application. She then kisses him but he pushes her away, apologizing. She slaps him twice and leaves.
Soo-rin arrives at the columbarium and puts the knife behind Jung-won’s father’s ashes. Locked in a cell, Jung-won grows distraught. The police find the knife in due time. But Tae-heon is also there and he shows them footage that proves Soo-rin kept it there. He’s reinstated immediately and the police rush to the airport to catch Soo-rin. Tae-heon arrests her just in time.
Later, Tae-heon visits Jung-won and gets her out of prison. He informs Woo-jae as well. Assembly manMo and Seol Pan-ho are having tea at the assemblyman’s house. Each taunts the other and Soo-rin’s fate is soon revealed. Jung-won and Tae-heon talk and the detective promises to put Yoon-young behind bars as well. He reveals Woo-jae set up the tip about Soo-rin. Jung-won leaves the station and faces all the reporters, where she apologizes. No Ji-ho questions her and she admits everything about fleeing the scene to save her position on the 9 o’clock news show.
Woo-jae is waiting for Jung-won nearby and takes her home. She falls asleep on the way and says Tae-heon’s name when Woo-jae tries to wake her. Later, Tae-heon interrogates Soo-rin. He brings up an entry from her diary in 2009. We see young versions of Soo-rin and Yoon-young standing by the dead body of another girl – Lee Na-ri. They set fire to the place, which is none other than the Bongto chemical plant.
At present, Tae-heon says Jin Myung-sook’s blood is on the diary. Soo-rin killed the housekeeper because she took the diary. A flashback shows the confrontation, where Soo-rin stabs Jin Myung-sook. While she’s looking for the diary, Cha Geum-sae enters and steals the bag of money. Tae-heon moves on to Eun-sae’s murder and a flashback shows Soo-rin approach the actress and suddenly stab her. Tae-heon tries to get Soo-rin to admit that she did everything on Yoon-young’s orders. However, the young woman starts shaking and falls down, prompting the police chief to stop the interview.
Yoon-young meets with Assembly man Mo and tells him to give her a suitcase full of money. She’s smug and says it’s not her fault that Soo-rin loves her.
The police team keeps getting more frustrated as Soo-rin refuses to say a word. Jung-won isn’t sitting on her hands though. She meets Kang In-han, her boss and asks why he suspected Assembly man Mo of the murders. Jung-won says the politician’s silence means that Yoon-young has something on him. In-han reveals that Assembly man Mo’s wife fell down the stairs thirteen years ago and has been in a vegetative state since then. He implies there’s more to the case.
While reporters crowd around Assembly man Mo, Jung-won confronts him. He plays a voice recording of a conversation between Yoon-young and Soo-rin where they openly discuss the crime. He also reveals that Yoon-young witnessed Soo-rin pushing her own mother down the stairs. Further, he reveals a scar on his body and says that Soo-rin tried to kill him too. Finally, he asks everyone to help catch Yoon-young. An angry Yoon-young calls Assembly man Mo afterwards and accuses him of presenting himself as a victim. He says it’s all over and puts the phone down. Yoon-young begins to walk into a lake, thinking of Woo-jae.
Tae-heon shows Soo-rin the clip of her father. She says she never tried to kill her father. When Tae-heon reveals that it was Yoon-young who got her caught, she screams in frustration. Jung-won goes home but is suddenly attacked by Yoon-young, who injects her with something. She collapses and the episode ends
