Barbie plays Lumina, a mermaid girl with the power to change the color of pearls. Cheerful and creative, Lumina finds herself working in a mermaid salon customizing fabulous hairstyles. And when Lumina has the chance to attend the royal ball, her friends adorn her with a gown fit for a princess. At the ball, villains try to seize power over the kingdom, and Lumina finds within herself an unexpected power that proves she is much more than a hair stylist.