After Sofia helps a little mermaid named Oona, Sofia's amulet grants her the power to transform into a mermaid and visit her new friend's secret underwater kingdom. But when Cedric plots to steal Oona's enchanted Mermaid Comb, danger surfaces for both worlds. With a little help from special guest, Princess Ariel, Sofia embarks on an adventure to rescue Oona and prevent a typhoon before it₂s too late.

Sweet, awkward sixteen-year-old Ruby Gillman is desperate to fit in at Oceanside High, but she mostly just feels invisible. She's math-tutoring her skater-boy crush, who only seems to admire her for her fractals, and she's prevented from hanging out with the cool kids at the beach because her over-protective supermom, has forbade Ruby from ever getting in the water. But when she breaks her mom's #1 rule, Ruby will discover that she is a direct descendant...

Mankind can no longer reproduce because of gene manipulation aimed at making life longer. The clones ruling the bottomless underworld may have become fertile. Parton is selected to go on a mission through a subterranean labyrinth crawling with monsters to secure humanity's future.