Single mom Young-eun starts to navigate her daughter So-hyun's mental health challenges after a series of tragic events. Despite her mom's earnest efforts to address So-hyun's mental disorder, her peculiar behavior persists. Two decades later, Min meets a new colleague, Hae-young, and they form a close bond. However, as Hae-young warmly integrates herself into Min's life, Min begins to feel uncomfortable and suspicious about her intentions.