Now holding the White, Black, and Purple pearls, mermaid Princess Mira continues her quest to break the curse that lies across her kingdom. The journey takes her, Clyde the merman, and Olena the octopus, through dark waters far from their home. Now sea creatures have begun to seek Princess Mira's pearls in earnest. An encounter with an unfriendly orca pod endangers their mission, and Mira must trust her friends to help her. Encounters with even more terrible beasts send them fleeing from the many who want her necklace at all costs. Only Princess Mira's determination to save her friends and her people keep her going through a journey that is growing harder.

But the guardian of the Blue Pearl is the most terrible beast of all, and Princess Mira must come to terms with her fears if she is to get the fourth pearl.

Friendship and seeing past appearances make this tale one young readers will return to again and again.