Far out in the ocean live the Shell-Keeper mermaids. While the rest of the world sleeps, one little girl joins them for some magical mermaid adventures. Molly can't wait to return to the Undersea Kingdom as a secret mermaid. Swimming with dolphins and diving for treasure is so exciting! But first, Molly must help her mermaid friend Ella find her missing enchanted shell - before it falls into the Dark Queen's evil clutches.