4 ideas
Criminal psychologist Seon-kyeong is summoned by imprisoned serial killer Lee Byeong-do, who refuses to talk to anyone but her. In the same period, her husband's eleven-year-old daughter Ha-yeong comes to live with them after her grandparents die in a house fire.
A specialist trained to detect pathology cannot switch that training off at home. Once the diagnostic frame is primed, ordinary ambiguous behavior in a child, such as silence, composure, or an odd remark, gets sorted into warning-sign categories. The expertise that makes the observer credible also makes her perception less reliable, because every datum now arrives already interpreted.
When a captive subject chooses his interviewer and decides what to reveal and when, the power in the interview reverses. The killer paces his disclosures to draw the psychologist into his narrative and to study her reactions. She ends up being the one who is examined and changed by the exchange, while he stays the one in control.
A stepparent who fears a partner's child is left with no legitimate way to say so. Voicing the fear sounds like rejection or jealousy, so the partner defends the child and dismisses the concern. The suspicion then goes private and unchecked, which makes it more intense and harder to test against anyone else's view.