Hyun-Jae, a 16-year-old escaping her abusive father, manipulates Hae-In, a woman searching for her missing daughter, into taking her in as a replacement. Over the summer, Hyun-Jae bonds with Hae-In, finding peace through her love for singing, but becomes obsessed with becoming Hae-In's new daughter. When Hae-In learns her missing daughter may have been found, Hyun-Jae, despite her fears, makes a selfless decision to accompany her, realizing she can't replace Yun-Seul.