The episode begins in 2019, where Kang Tae-joo, a former detective now turned teacher, meets his former colleague, Chief Inspector Lee Sun-kyung. Sun-kyung informs Tae-joo that the culprit of the Kangseng serial murders, a 30-year-old case, has finally been arrested. This leaves Tae-joo shocked and deeply affected. She explains that during their earlier investigation, the serial killer, Lee Yong-woo, was already serving time for killing his sister-in-law. Sun-kyung reveals that the police were only able to find Yong-woo’s DNA in three cases and are trying to get him to confess to the rest. Tae-joo is shaken and expresses his doubts about obtaining a confession.
Sun-kyung then asks for Tae-joo’s help, saying that the culprit himself has requested him. Tae-joo goes home and takes out the case files, noticing a scarecrow figurine inside.
The episode shifts to 1988, where a young detective Tae-joo is transferred from Seoul to his hometown, Kangseng, for making a public spectacle out of Sergeant Choi Jung-mo’s arrest on charges of bribery. Tae-joo’s friend and news reporter, Seo Ji-won, questions Police Commissioner Park about the allegations against his nephew, Jung-mo.
That night, Tae-joo drives back to Kangseng, meeting his friends Ji-won and Lee Ki-hwan. The three share food and drinks, and the locals are shocked to see Tae-joo back in town. That night, Ji-won and Ki-hwan bring a drunk Tae-joo home and ask his sister Sun-young to put him to bed. In the middle of the night, Tae-joo wakes up from a nightmare about being bullied as a teenager.
The next day, Tae-joo arrives at the station where the detectives treat him coldly. They call him a city snob and ignore him. He speaks to rookie officer Park Dae-ho about his time in Seoul.
Tae-joo sees Seong-jin in custody and becomes angry when he notices the man has been beaten badly. He warns Myung-do and Hyung-gu about the consequences, but Detective Kim Man-chun tells him that Seong-jin is a murderer.
Meanwhile, prosecutors meet to discuss the murder of Kim Bok-hee. Prosecutor Cha Si-young is praised for arresting Seong-jin, while Hwang Jae-hoo is criticized. After the meeting, Jae-hoo speaks to Si-young and asks him to get a confession. Si-young meets Myung-do and Hyung-gu to confirm details and becomes upset when he learns that the investigation was poorly handled. He asks to question Seong-jin himself.
Elsewhere, Tae-joo looks into Seong-jin’s case file and learns that he was previously imprisoned for indecent assault. Dae-ho says this is Seong-jin’s first murder charge, but Tae-joo tells him not to jump to conclusions. While searching for Bok-hee’s case file, Dae-ho drops crime scene photos, and Tae-joo realizes they may be dealing with a serial killer.
Tae-joo confronts Seong-jin, who initially claimed innocence but now admits to the murder. Hyung-gu steps in and asks Tae-joo to step back as Seong-jin is officially charged. Later, Tae-joo learns that Si-young pressured Seong-jin into confessing.
In a flashback, Si-young accuses Seong-jin of killing Bok-hee with stockings and threatens him with a harsher sentence if he refuses to confess, offering a lighter one if he agrees. Worried about his family, Seong-jin agrees. As Si-young leaves, Tae-joo realizes that the man who bullied him in school is the same person. Although shaken, Tae-joo regains his composure.
Back at the station, detectives discuss Tae-joo's interaction with Si-young and invite him out for drinks, but he refuses. Instead, he stays back and continues investigating, trying to connect the murders through a pattern. Ji-won arrives and attempts to look through the files, but Tae-joo takes her out instead.
Elsewhere, a high school student, Yu Jeong-rin, approaches local heartthrob and Ki-hwan's brother, Lee Gi-beom, at the library. Later that night, she and her friend Min-ji walk home when someone runs toward them. They split up, and Jeong-rin is abducted by a mysterious man.
The next day, Seong-jin is taken to a crime scene reenactment. Tae-joo refuses to join the spectacle and goes to the prosecutor's office to meet Jae-hoo. There, he runs into Si-young again, who mocks him for being transferred back to Kangseng. Tae-joo ignores the man and meets Professor Jae-hoo.
Tae-joo tells Jae-hoo that the murders are connected and likely committed by the same person. He explains that Seong-jin cannot be the culprit because he was in prison during the first murder. Jae-hoo is uncertain about the comment. Tae-joo explains that the killer is escalating based on the investigation details and that he will strike again.
Soon after, the police receive news of another body. Tae-joo and Dae-ho rush to the scene, where Jeong-rin is found dead in the same manner. At the prosecutor's office, the chief reprimands Si-young for mishandling the case. Jae-hoo presents Tae-joo's findings and argues that a serial killer is responsible. Si-young refuses to accept this, but the chief allows Jae-hoo to lead the investigation. Filled with rage, Si-young becomes determined to prove Tae-joo wrong.
Back at the station, Min-ji tells Tae-joo and Dae-ho that she saw a man named Kim Han-seop chasing a woman with a knife on the night of the murder. The police arrest Han-seop as he threatens the same woman with scissors. He claims she is his wife and says he was trying to bring her back home. His wife confirms that he forced her but also recalls seeing Jeong-rin and Min-ji that night. She mentions seeing a scarecrow nearby that later disappeared. This detail strikes Tae-joo, especially since Min-ji mentioned the same thing.
Meanwhile, Min-ji sketches the scarecrow she saw. Tae-joo returns to the crime scene, finds a scarecrow cap, and pieces together the pattern. He concludes that the killer disguised himself as a scarecrow in the fields and waited for Jeong-rin to be alone before attacking. He runs into Si-young there who says he will take the case back. Tae-joo confronts him and calls him out for bullying him.
The episode ends with present-day Tae-joo going to the prison facility to meet the killer he has been chasing all this while.
