Sofia Ruiz adores her horse, Sundance, a gift from the grandmother who has cared for her during her mother's absence. Weeks before her eleventh birthday, her mother demands that she pack her things, forcing Sofia to leave Sundance behind. She's sent to live with the great-grandfather she barely knows. Anxious, lonely, and determined to be reunited with Sundance, Sofia searches for a way to return to her grandmother. After meeting the neighbor's miniature horses, Sofia is invited to join the Mini Whinnies Horse Club with quick-tempered Olivia, who uses crutches to walk, and her twin brother, Ryan, who's afraid of horses. As her horse and human friendships grow, Sofia wrestles with where she belongs. Will she ever see Sundance again?