Jung-hwan and Yong-soo visit Ha-bin at her place to interrogate her and see Tae-soo there. Tae-soo goes around trying to check Ha-bin's alibi on the 11th. He finds dashcam footage of Ha-bin that goes against her alibi. Ha-bin suggests to Tae-soo that they move, but Tae-soo insists on staying until he catches the real culprit. Meanwhile, cops find a stash of cash in Tae-soo's car and accuse him of accepting bribes.

A chilling discovery unfolds as a seemingly innocent keyring from Ha-bin reveals the possibility of a serial murder case. Tae-soo grows increasingly anxious, sensing that Young-min and Ha-bin are hiding something crucial. Just as the tension rises, the police arrive at Tae-soo's home once again, intensifying the fear of what secrets might be uncovered.

Tae-soo gets a call from his wife, who died one year ago. As Tae-soo learns about Ji-soo's shocking secret, Joon-tae becomes increasingly apprehensive as the investigation progresses. Meanwhile, Ha-bin, who believes her mother is a murderer, begins to dig deeper into her mother's past as an unidentified man follows her from behind.