Andi Mack is a 13-year-old girl who discovers that her older sister, Bex, is in fact her mother. This unexpected revelation causes Andi to begin an uncharted course of self-discovery, with her best friends by her side.

Now Andi and her overprotective grandparents must learn to adjust to having Bex in the picture. And when Andi's father arrives to meet the daughter he never knew existed, Andi is one step closer to getting her picture-perfect happy ending.