The fifth episode begins with a flashback to Jeong-woo’s younger years. He ignores his mother’s request to not drive and playfully continues to take the car out. The scene changes to the current moment as Jae-hee confesses to Gu-tak that they were responsible for Bo-young’s death.
Another flashback shows Bo-young catching her mother having an affair with Gu-tak on the day of her murder during a visit to him. Bo-young runs away and arrives at the warehouse.
Jae-hee, in the current time, requests Gu-tak to do her a favor by releasing Dong-min from jail. Gu-tak resists obeying, leading Jae-hee to menace him with revealing his secrets.
In the meantime, Jeong-woo attempts to retrace his movements from the evening that resulted in Da-eun going missing and Bo-young being killed. He comes to the decision that the car had insufficient fuel for him to make it back from the deserted school that evening after getting rid of Bo-young’s body. At the police station, Byeong-moo becomes upset as Sang-cheol attempts to reopen the case for further investigation. Inquiring about Da-eun makes him feel anxious. Sang-cheol is aware of this but does not go into detail.
In the meantime, Ha-seol reflects on her day and comes to the realization that Su-oh likely saw the murders and was an important witness aware of what transpired that evening. He reviews the interrogation video to track Jeong-woo’s movements on the night of the incident.
By chance, Jeong-woo hails a taxi to the spot where Bo-young’s body was discovered and attempts to follow his own path to figure out how he may have been trying to get rid of her body. Upon reviewing the case reports, Sang-cheol determines that it is not feasible for Jeong-woo to have both disposed of Bo-young’s body and killed Da-eun simultaneously.
Jeong-woo also came to the conclusion that he was unable to go back to the warehouse and ended up killing Da-eun that evening. Sang-cheol heads to the warehouse and encounters Jeong-woo. Both men talk about how Jeong-woo was unable to commit both murders when Ha-seol arrives. According to her, Su-oh had depicted the crime scene in one of his artworks.
Sang-cheol claims that Su-oh’s credibility as a witness was compromised by his neurological condition. Ha-seol asserts that she will come back with the painting to convince Sang-cheol of her point and make him depart. That evening, Jeong-woo returns to the hospital and has an emotional collapse, reflecting on the years of suffering he and his family endured.
The following morning, Na-kyeom arrives at the hospital and visits him, but he attempts to reject her. She remains steadfast and insists on eating a meal with him. While eating, Jeong-woo informs Na-kyeom that Da-eun was murdered and Bo-young’s body was disposed of simultaneously. He says he plans to go to the police station and request the officers to reconsider the case.
Simultaneously, Byeong-moo assists Jae-hee, Choo-ho, and Heung-soo in meeting with Dong-min to plan for Bo-young’s funeral following the discovery of her remains. Jae-hee and Dong-min have a disagreement, leading him to threaten physical violence, prompting her departure. Ha-seol encounters Gu-tak when he appears at the restaurant to join Heung-soo and Choo-ho.
They talk about Bo-young’s upcoming funeral and how Jeong-woo managed to locate her body. Gu-tak tells the men to go away from Jeong-woo and mentions that he will attempt to convince Jeong-woo to depart from the town. He also requests Choo-ho to dismiss Ha-seol as a personal favor. That day, Ha-seol encounters Hyung-sik and attempts to find out about Su-oh’s situation. She tries to meet him but Hyung-sik claims he is not in the best condition to meet her.
Ha-seol requests for Hyung-sik to inform her of when she can see Su-oh before departing. While returning, Ha-seol notices a man resembling Su-oh. The man steps out of the taxi and goes into Gu-tak’s residence. Meanwhile, Sang-cheol encounters the police at the station and discusses the inconsistencies he discovered during the investigation.
This angers Section Chief Hee-do, but Gu-tak informs Sang-cheol that the case cannot be reopened without new evidence. Jeong-woo arrives at the station and requests the police to reinvestigate the case, but Gu-tak declines. Gu-tak requests a private conversation with Jeong-woo and urges him to cease his efforts to have the case reopened.
He explains that being a friend of Jeong-woo’s father, he made every effort to ensure Jeong-woo would not receive a harsher punishment. Gu-tak goes on to say that reopening the case at this moment will only escalate the situation. Just as Jae-hee is texting Gu-tak to release Dong-min, Jeong-woo leaves, threatening him.
Gu-tak watches the interrogation video of Dong-min and accuses Sang-cheol of using unethical methods to force a confession out of him. He requests Hee-do to free Dong-min because of this and phones Jae-hee to inform her of Dong-min’s release. After Dong-min is released from prison, he contacts Choo-ho and requests him to hire a hitman.
Meanwhile, Assemblywoman Young-sil is anticipating Hyung-sik’s arrival for dinner at a nearby restaurant. The visitors applaud her and snap photos with her, expressing gratitude to Young-sil for her excellent service. That evening, Dong-min encounters Choo-ho and Heung-soo. Heung-soo advises Dong-min to reconsider his choice to eliminate Jeong-woo, but the other two men urge him to withdraw from the plan.
Meanwhile, Jeong-woo encounters Sang-cheol at a bar and they converse about the reasons for reopening the case. Sang-cheol says he wasn’t part of Jeong-woo’s team but aims to re-investigate the case to capture his partner. Jeong-woo mentions that he visited the warehouse that day due to his frustration towards Da-eun declining his phone call. He informs Sang-cheol that he believed Da-eun was being unfaithful to him.
Sang-cheol informs Jeong-woo that they cannot open the case again unless they have new evidence. During dinner, Young-sil engages in a conversation with Hyung-sik about work and inquires if he is feeling stressed due to Su-oh. He apologizes and goes to the restroom, where he unexpectedly meets a female patient. Young-sil decides to look through Hyung-sik’s phone and discovers a message that shocks her.
Simultaneously, Heung-soo is fearful when he is near Byeong-moo. Dong-min visits Jeong-woo’s residence armed with a weapon with the intention of ending his life. Ha-seol notices that the light is on in Su-oh’s bedroom and requests to meet him. Gu-tak arrives, escorts Ha-seol to Su-oh’s room in order to demonstrate he is still at the hospital.
Upon leaving, they encounter a man resembling Su-oh, causing Gu-tak to be surprised. When Jeong-woo arrives home, he sees Dong-min inside his house. Dong-min aims the gun at Jeong-woo, but Jeong-woo remains unfazed as the scene concludes with the sound of a gunshot.
Watching this episode was very exciting because the show revealed a major plot twist – it’s possible that Su-oh has a twin brother. Su-oh’s twin is likely the one who sexually assaulted and murdered Bo-young, while another person may have caused Da-eun’s death or disappearance. Because her body has not been located, it can be surmised that she is still living and is a person who possesses the solutions to all the queries that this episode has presented us.