When Cedric and Sofia are tasked with babysitting Zinnia while her parents are summoned to Princess Ivy's old homeland for a few days, the little girl has a hard time adjusting to the castle. To get her mind off her homesickness, Sofia decides to give an old method a new and magical update: telling Zinnia, as well as some of the other children, an immersive story via the Secret Library. The story? "The Little Mermaid," but with an ah-mazing Sofia-style twist.