When Molly Holmes moves with her family to Horseshoe Bay, her grandmother gives her an enchanted shell necklace that magically transforms her life. The power of the necklace transports Molly to the Undersea Kingdom, where she discovers that she is a Secret Mermaid and meets lots of new mermaid friends. But the evil Dark Queen Carlotta seeks to steal control from the good Merqueen Luna, by seizing the magic pieces of conch shell that help protect the...

Casper, the cocky new boy at magic school, challenges Oliver Moon to a scary spell-off, and Oliver is worried even his trusty magic wand will not help him get out of trouble.

Oliver Moon thinks his luck is in when he wins the Magic School raffle, until he's presented with his prize - a hideous painting of an ugly monster. But could there be more to the picture than meets the eye?

In the climax to the mermaids' search for their pieces of the magical conch shell, Molly finds herself in the frozen seas of the Arctic. There she discovers that the Dark Queen has stolen the last conch piece and imprisoned ice mermaid Shivana. With the help of a friendly walrus, Molly rescues Shivana, and, dodging an attack by an enchanted polar bear, they set off to confront the Dark Queen in her distant lair.

"Swimming with the turtles and tropical fish in the ocean reefs has always been such fun for the mermaids, until the reefs begin to die. Molly must help her friend Coral find her magic shell so she can rescue the reef -- but the wicked Dark Queen and her army have other plans..." -- Back cover.

Barney is having a wonderful time with Grandpa. Will the two of them ever get to sleep?

Molly must venture into the ocean's darkest depths to help find mermaid Pearl's missing shell. They know the Dark Queen's sea snakes are on the prowl - but nothing can prepare them for the discovery that Pearl's shell is inside a huge underwater volcano - a volcano that could erupt at any time!

Molly is called back by the Mermaid Queen because the mermaids desperately need her help. All the whales, turtles, seahorses, octopuses and dolphins have vanished from the seas and the mermaids expect dark magic is at work. Molly believes the answer to their whereabouts might lie in a strange sparkly ball she spotted in a rock pool.

Many sea creatures have suddenly gone missing and Molly is determined to help her friends find them all. The seals have reported hearing strange, distant dolphin noises, so Molly and Aisha go to investigate. When they discover a magical shell with the thousands of tiny dolphins trapped inside, they have no idea how to release them.