In the third episode of The Scarecrow, Tae-joo visits Yong-woo at the prison to discuss his unwavering dedication to solving the Kangseng Serial Killer case, which has become his life's mission. This revelation leaves Yong-woo perplexed, as he does not perceive a similar sense of purpose in his own life.
The episode then shifts back to 1988, where Tae-joo learns that Jae-hoo has transferred the investigation of the serial killer to Si-young. Despite being threatened, Tae-joo refuses to cooperate with the prosecutor. The Police Chief attempts to persuade Si-young to reinstate Tae-joo, but Si-young demands that he resign. The Police Chief considers this, but Man-chun intervenes, reminding them of Tae-joo's heroics in saving a woman from being kidnapped and potentially murdered. Si-young relents but removes Tae-joo from the investigation.
Upon his release, Tae-joo rushes to the hospital and finds Sun-young by Ji-won's bedside. Ji-won remains unconscious, and Tae-joo questions Sun-young about the incident with Kyung-ho. Sun-young explains that Kyung-ho brought up their mother's past, leading to the altercation. Tae-joo feels relieved that she is safe but blames their mother for their struggles. Sun-young defends their mother, and the two argue.
Tae-joo leaves the hospital and recalls seeing their mother with another man when he was younger. The memory continues to haunt him, but Tae-joo rushes to meet Jae-hoo. He learns that Si-young blackmailed him into handing over the case. Jae-hoo reveals that his son is being used against him.
That night, Si-young goes to Sae-beom's club, Modako, with Kyung-ho. Tae-joo follows and secretly records their conversation using a waiter as an intermediary. Inside the club, Sae-beom gives Kyung-ho a VIP pass while Si-young discusses the case. Si-young instructs Kyung-ho to lie about having an affair with Sun-young to weaken the assault accusation.
The next day, Gi-beom's mother and sister-in-law visit Sun-young in the hospital. Kyung-ho's wife arrives and publicly accuses Sun-young of having an affair. Sun-young denies the allegations. In private, Gi-beom's mother urges Sun-young to end the relationship, citing her mother's past as a character flaw. Unaware of this, Gi-beom continues to consider marrying Sun-young.
Meanwhile, Kyung-ho returns to Modako with the VIP pass and brings his friends along. He behaves arrogantly, which angers Sae-beom. Sae-beom refuses to tolerate it and complains to Si-young.
Si-young discovers the recorder and reacts violently, accusing Sae-beom of betrayal. Sae-beom denies involvement and promises to find the culprit. Meanwhile, Ji-won regains consciousness and tells her brother Un-hui about the camera. Un-hui and his friend search for it but fail to locate it. At Modaku, Sae-beom finds the waiter who planted the recorder and threatens him. He informs Si-young that Tae-joo is behind the attempt.
Back at the station, since Tae-joo cannot officially work on the case, he uses Dae-ho to question the first victim, Kim Mi-yeon. She reveals that the attacker claimed to have killed five women. Tae-joo realizes there is another victim whose body has not yet been found.
The team reviews missing persons reports to identify the possible victim. Si-young arrives and offers Tae-joo a deal: he will reinstate him if Sun-young withdraws the assault case against Kyung-ho. Tae-joo refuses and proposes a counteroffer: he will continue searching for the fifth victim and resign if no body is found. The Police Chief supports this plan, seeing an opportunity to shift responsibility. Si-young agrees to the arrangement. That night, Tae-joo identifies a missing woman, Choi In-sook, as the likely fifth victim. The next day, he and Si-young visit her home.
In-sook's mother is convinced that her daughter ran away after a heated argument. Tae-joo, uncertain of the situation, requests a search operation. Si-young approves the search and informs the Police Chief. Meanwhile, Sun-young learns of Tae-joo's arrest and feels shaken. Ji-won reassures her, telling her that Tae-joo truly loves her but is unable to express his true feelings for his sister.
Later, Sun-young asks Tae-joo to visit her more often. Tae-joo feels uneasy and checks on Ji-won instead. Ji-won scolds him for letting the suspect escape and mentions the photograph she took. That night, Ji-won awakens from a nightmare about the attacker. Un-hui arrives with an urgent file sent to the newsroom. The file contains a cassette tape addressed to "Tae-joo's friend."
The next morning, Si-young picks Tae-joo up for the search operation. He mocks Tae-joo, suggesting he will resign if the search fails. Reporters gather as they arrive at the site. Kyung-ho and his uncle, the governor, appear and accuse Tae-joo of abusing his authority. The situation steals public attention away from the investigation.
Meanwhile, Ji-won arrives and publicly plays the cassette tape. The recording exposes Kyung-ho discussing falsified records and inappropriate behavior. Kyung-ho reacts angrily and stands from his wheelchair, attempting to attack. The governor is embarrassed by his nephew, but Tae-joo loses his temper when he hears Kyung-ho speak about Sun-young suggestively. Si-young stops Tae-joo as the governor and Kyung-ho leave. The search operation resumes while Ji-won indirectly thanks Si-young for handing over evidence in favor of Tae-joo. The search team finds In-sook's belongings, which Tae-joo returns to her mother. Mrs. Choi passes away soon after, and Tae-joo pays his respects to the woman.
Back at the newsroom, Ji-won examines the blurry photograph of the suspect, which she uses to pressure him. Elsewhere, Gi-beom learns about Sun-young's assault and confronts her. He is hurt that Sun-young lied to him despite their engagement. Sun-young decides to end the relationship and breaks up with him.
Meanwhile, Tae-joo resigns and leaves the force, true to his word. He later visits the library, where he meets Min-ji. She is disappointed to learn about his resignation and urges him to continue pursuing the case. That night, Min-ji returns to the library to collect her art supplies. As she walks home in the rain, she encounters the killer. She tries to escape, but he catches up to her.
The next morning, Tae-joo receives news of another victim. He arrives at the scene and discovers that Min-ji has been killed. Overwhelmed by the incident, Tae-joo passes out at the scene. Episode 3 ends in 2019 with Tae-joo asking Yong-woo if he was the one who ruined his mission.
