The opening scene of Episode 1 of "The Price of Confession" unfurls at a wedding in 2017, where a man named Ki-dae ties the knot with a woman named Yun-su, who soon becomes a mother to a baby girl named Sop. The scene shifts to 2022, where Ki-dae is found stabbed in the neck in his studio. Yun-su frantically tries to stem the flow of blood while frantically dialing 911 for help, but to no avail. His funeral soon follows.
A few days later, Yun-su is summoned for questioning by Detective Ryu. She explains that Ki-dae had lost his parents long ago, and she herself has always been an orphan. On the day he died, she witnessed someone emerging from his studio, clad in a black hoodie. They had been planning to try for another child that night. Yun-su also mentions that a student named Oh Seo-won was present in the studio that day. However, Detective Ryu notices a suspicious bruise on Yun-su's wrist, and the other detectives find her unusually cheerful demeanor odd.
After a grueling interrogation, they decide to bring in Baek Dong-hun, an ex-cop turned prosecutor with a unique approach to cases. He sifts through the case files, which describe how Ki-dae was stabbed with a carving knife and how etching solution was poured over everything to destroy any evidence. Except for the knife itself, which was unscathed by the solution.
However, to everyone's surprise, Dong-hun lets Yun-su go. Before leaving, he tells Detective Ryu that he wants to take over this case. As Yun-su goes about her day, Baek Dong-hun follows her closely. That night, he watches her take pictures of her husband's belongings and post them on Craigslist – an unusual behavior for someone who has just lost her husband.
The next day, Dong-hun receives a call from Detective Ryu, who informs him that Yun-su wants something from her husband's studio but was not granted permission to enter it. While sifting through Yun-su's empty classroom, Dong-jun discovers a bill for etching solution.
Oh Seo-won, the student in question, is then brought into custody and accused of having an affair with Ki-dae. However, she insists that she left the studio at 5 o'clock and took a cab home. Despite this, Dong-hun allows Yun-su to meet her and watches as she confronts her about the affair.
Dong-hun returns to the crime scene, his mind reeling in confusion as to why the etching solution failed to mar the blade. He gathers all the carving knives from the studio and submits them to the forensic team, his quest for the truth unrelenting.
The detectives swiftly track down the taxi that ferried Seo-won, verifying her alibi. With her removed from the equation, Yun-su stands as the sole remaining suspect, and she is soon arrested. That night, Dong-hun delves into a trove of videos found on Yun-su's USB drive, revealing intimate moments between her and Ki-dae at home. As he grills Yun-su on the fateful day, she claims ignorance of Seo-won and Ki-dae's connection.
Yet, side by side, we witness Yun-su enter the studio, her path marked by telltale signs of an affair – condom wrappers among them. She strikes Ki-dae on the head with a bottle of wine she purchased and then plunges the carving knife into him. Is this a genuine flashback? Or merely an enactment of Dong-hun's imagination?
Dong-hun extracts the carving knife that was indeed used to slay Ki-dae, accusing Yun-su of replacing the knives to divert suspicion towards Seo-won. He charges her with a desire to return to the studio with the intention of snatching the real knife and concealing it.
Moreover, he unearths records from the orphanage where Yun-su grew up, detailing how she pushed a friend down the stairs when they were 12 years old – all because the other girl's face was featured on milk cartons at school. He contrasts this with a loving letter penned by Yun-su's current students, who implore the police of her non-violent nature. He confronts her with the question: Who is the real Yun-su?
Yun-su's words fall on deaf ears, and she is sentenced to prison. Meanwhile, Dong-hun's boss instructs him to allow the media to cover the schoolteacher's case, as it would serve as a distraction from another fraud case involving several high-ranking individuals. We then see journalist Hong, playing the private videos of Ki-dae and Yun-su, revealing instances where Yun-su casually threatened to end his life.
As Yun-su bids farewell to Ki-dae over the phone while exiting school, the air crackles with anticipation for their evening of bonding at Sop's sleepover. Hearing Seo-won's voice in the background, Yun-su urges her friend to usher her off the line, eager for their private time together. She grabs a bottle of wine, her heart racing, and makes her way to the studio. As she prepares in the car, a hooded figure exits the studio, casting a shadow of unease. Stepping inside, she finds her husband lying in a pool of blood, the bottle of wine clattering to the ground.
Meanwhile, in a sleek glass house, Mo-eun watches the news with a smirk, her surroundings adorned by two lifeless forms. The report details Yun-su's trial and her life sentence, as Yun-su's protestations of innocence echo through the airwaves. Mo-eun's smile widens as she sees the images of Yun-su's plight, her eyes fixed on the screen with a mix of glee and disdain.
