Five-year-old Mia is at the supermarket with her mother, Lori. To comfort Luna, the daughter of a coworker fighting cancer, Lori makes Mia call her "Auntie" in public and tells the cashier Mia is just a cousin's kid. She swears it's a one-time thing, but again and again, Lori gives Luna the love and attention meant for her own daughter. Hurt, Mia quietly pulls away and starts calling her mother "Auntie," a change that spreads through the neighborhood and her preschool. Her father, Beckett, sees the wound and quits his out-of-town job to come home. When Lori brings Luna to the Mother's Day event instead of Mia, it breaks her last hope. At a community talent show, Mia speaks her pain out loud. Beckett documents the neglect, files for divorce, and wins full custody. Then Iris, his longtime friend and bakery partner, gently steps in, and Mia finally finds a home where she's truly cherished. Lori is left alone with her guilt.
