In Episode 6 of The Scarecrow, set in 2019, Tae-joo embarks on a personal meeting with Young-woo. During their conversation, Young-woo confesses that he is responsible for 14 murders, not the nine initially believed by the police. Despite agreeing to confess, Young-woo instead requests to hear more about Tae-joo's personal story in exchange for the truth behind one of the murders.
The episode then shifts back to 1988, where Tae-joo discovers that Gi-beom was present with him on the night of In-sook's kidnapping. He promptly meets with Si-young and implores him not to publicly declare Gi-beom as the suspect during the upcoming press conference on the serial murders. Although Si-young initially agrees, he changes his mind upon seeing his father at the conference. Under pressure, Si-young officially names Gi-beom as the prime suspect, causing widespread panic across the city.
Sun-young, Gi-beom's family, and Ki-hwan are all left disappointed in Tae-joo, while Jun-young is upset with Si-young for going directly to the media. Meanwhile, Tae-joo visits a clinic where he meets Dr. Jo Yun-seok, a nuclear scientist. Dr. Jo introduces Tae-joo to radiotope analysis and suggests using hair follicles to identify the suspect. Tae-joo becomes fascinated by the idea but shifts his focus after seeing a news report where Si-young publicly identifies Gi-beom as the main suspect in the serial murder case.
Elsewhere, Si-young's father pressures him into setting a wedding date with Hee-jin due to uncertainty surrounding the upcoming elections. Tae-joo interrupts Si-young's office meeting and requests a private conversation. After Mu-jin leaves the room, Si-young reveals that the victim's body was badly decomposed when discovered, making the autopsy timeline unreliable. He also learns about Sun-young's pregnancy and assumes that Tae-joo is desperately trying to protect Gi-beom because of it. Tae-joo argues with him, but Si-young insists that Tae-joo produce the real killer if he is so certain about Gi-beom's innocence.
At the same time, Myung-do and Hyung-gu violently beat Gi-beom during questioning. Si-young arrives and accuses Gi-beom of being a communist based on the radical books sold at his bookstore. He also threatens to arrest Ki-hwan. In response, Gi-beom offers to tell Si-young the truth if he agrees to leave his brother alone.
The following day, Tae-joo meets Dr. Jo at the research center and asks him to analyze the hair sample collected from the handkerchief. Dr. Jo discovers large traces of titanium along with sodium and chlorine in the sample. Based on these results, he concludes that the suspect likely works in a metal-related factory and sweats heavily while working.
Meanwhile, Ki-hwan sends his wife away to stay with her parents temporarily for safety. Tae-joo later visits the bookstore after realizing that Gi-beom's blood type does not match the suspect's. Hoping to secretly test Ki-hwan's blood, Tae-joo tries to collect a sample after Ki-hwan accidentally cuts his hand on broken glass. Ji-won catches Tae-joo in the act and stops him immediately. Hurt by Tae-joo's lack of trust, Ki-hwan angrily hits him.
Later, Tae-joo reveals his belief that the true killer is someone close to Gi-beom. He visits Ilwon Industries to meet Gi-beom's friend, Lee Jung-soo, and discovers that Jung-soo's blood type is O. Coincidentally, Gi-beom is formally taken into custody as the suspect in the serial murders. Myung-do and Hyung-gu inform Tae-joo that Gi-beom has already confessed to all the murders. Sensing something amiss, Tae-joo requests a private conversation with him. However, Gi-beom persists in his claim of being the killer. Frustrated, Tae-joo storms out of the interrogation room and encounters Sun-young, who blames him for pressuring Gi-beom into lying. Tae-joo vents his emotions before leaving and tells his sister to abort their child. Ji-won stays behind to comfort Sun-young.
The next day, Jun-young pushes for the creation of a special investigation team to prevent Si-young from gaining full control of the case. Around the same time, Si-young visits the police station and finds Sun-young speaking with Dae-ho. She asks Si-young for permission to meet Gi-beom once, and he reluctantly agrees.
During their conversation, Sun-young reveals her pregnancy and begs Gi-beom to change his confession. However, Gi-beom refuses to retract his statement and instead asks her to stop accepting help from Si-young. Sun-young promises that she will continue waiting for him no matter what happens.
Meanwhile, In-sook attempts to identify her kidnapper through his voice. She listens to a conversation between Gi-beom and the police officers but fails to recognize him as the culprit. Myung-do dismisses her concerns and orders her to leave with her belongings.
Ji-won later finds In-sook and speaks with her. In-sook reveals that she discovered a matchbox inside her bag that does not belong to her. At the same time, Tae-joo compares Gi-beom's official confession with Mi-yeon's earlier statement and notices several contradictions. He barges into the interrogation room and catches Myung-do and Hyung-gu brutally beating Gi-beom again.
After seeing Gi-beom's injuries, Tae-joo realizes that the confession has been forced through violence. He becomes furious after learning that Si-young is fully aware of the torture and still ordered Gi-beom's arrest.
Meanwhile, Mu-jin and Si-young meet with Hee-jin's parents and finalize wedding plans after the elections. Chairman Kim encourages Si-young to move to Seoul because of his recent achievements. Later that night, Mu-jin drops Si-young home and notices Tae-joo waiting nearby.
In a flashback, we see Mu-jin having an affair with Tae-joo's mother. Tae-joo requests Mu-jin to drive him and Sun-young to the hospital, as Si-young observes their interaction silently.
Back in the present day, Tae-joo angrily punches Si-young for forcing Gi-beom to confess to crimes he did not commit. Si-young argues that Tae-joo's behavior is irrational, leading to a physical fight between them. Before leaving, Tae-joo promises to make Si-young pay for framing an innocent man for the second time.
Later, Si-young returns home and reflects on Tae-joo's accusations. The next morning, Tae-joo meets Jun-young and insists that Gi-beom is being wrongfully detained. He requests that Gi-beom be transferred to a hospital for treatment and vows to identify the real killer.
Meanwhile, Ji-won visits the cafe connected to the mysterious matchbox and questions the workers there. A woman reveals that a young man returned In-sook's purse after accidentally knocking her off her bicycle. She identifies him as the owner of a farm equipment repair shop.
At the same time, Tae-joo speaks with Gi-beom and learns that Seok-man witnessed Myung-do and Hyung-gu kidnapping him. Tae-joo later tracks Seok-man down and finds Ji-won there as well. He notices that Seok-man limps, works with metals, and sweats heavily while working. Tae-joo finally realizes that Seok-man matches the radiotope analysis profile and begins suspecting him as the real serial killer.
The episode shifts back to 2019, where Tae-joo tells Young-woo that he will reveal the identity of his lost friend later. Young-woo then asks Tae-joo to speak to him casually like they did in the past as the episode comes to an end.
