Mermaid Princess Mira now has both the White and Black pearls, which will help deliver her kingdom from its year-long curse. Now she must seek out the Purple Pearl, guarded by the Purple Fairy. With her friends Clyde the merman and Olena the octopus, she sets out through even more dangerous waters. But now creatures are interested in the necklace which holds the two pearls and are willing to harm Princess Mira to get it. An underwater cave holds unexpected dangers. Following glowing seaweed, they navigate through its tunnels, helped by some creatures, chased by others. But reaching the Purple Fairy is only the first step. Is finding the Purple Pearl an impossible task? This story of friendship and bravery will appeal to young readers with its courageous and intelligent heroine.