Thriller

Sleep Well, Mommy, also published in English as The Only Child, is a psychological thriller that explores the disturbing connections between childhood, violence, and the origins of evil. Seonkyeong, a criminal psychologist, receives an unexpected opportunity when Yi Byeongdo, a notorious serial killer who has refused to speak publicly, agrees to be interviewed by her. At the same time, her husband brings his eleven-year-old daughter, Hayeong, to live with them following the mysterious deaths of the grandparents who had been raising her. Seonkyeong initially tries to welcome the girl into their home, but Hayeong’s unsettling behaviour soon begins to trouble her. As Seonkyeong investigates the pasts of both the killer and her stepdaughter, she discovers disturbing similarities between them. The more she learns, the more she questions what she thought she understood about Hayeong and the circumstances surrounding her family’s deaths. Blending domestic suspense with criminal psychology, Seo’s novel examines the relationship between childhood trauma, family secrets, and the nature of evil.