Cha Woo-kyung is a devoted child psychologist whose life seems perfect until a sudden, tragic accident shatters her world. Plunged into a dark reality, she encounters a mysterious child and begins noticing enigmatic clues conveyed through lines of poetry, drawing her into a chilling series of events involving child abuse and murder. Alongside Kang Ji-heon, a fierce and relentless detective who strictly follows the law, Woo-kyung races to uncover the identity of a masked vigilante who targets abusers under the guise of poetic justice. As the investigation deepens, the boundaries between victim and perpetrator blur, forcing both Woo-kyung and Ji-heon to confront deeply buried secrets from their own pasts. The series offers a gripping psychological suspense thriller that questions society's failure to protect its most vulnerable children and explores the moral complexities of justice, guilt, and redemption.