So-eun, a police officer, is ordered to join a secret investigation. So-eun tries to negotiate with the kidnapper disguised as the victim's mother. However, the suspect seems to be getting through all the moves of the investigation team. The suspect’s meticulous plan makes the investigation difficult. Meanwhile, even So-eun's son is being kidnapped. As a police officer and a mother, she feels guilty for not protecting the kidnapped child and her child. Finally, she makes the biggest decision in her life. There is nothing to lose and nothing to fear. She starts a desperate punishment that goes beyond the limit.