Emily Windsnap has returned home to Brightport, but she can't help but miss the fantastical adventures she's been having on pirates ships and tropical islands. And Brightport isn't exactly welcoming her home either - in fact, her best friend Mandy doesn't seem at all happy to see her. At least she has a new wishing stone, which will grant her three wishes, to help make things better. But whatever Emily wishes seems to end badly. When she wishes for things to improve in Brightport, it has terrible consequences for her mermaid friends in the ocean. And when when she wishes for the ocean to be kept safe, life on land becomes impossible. Can Emily work out how to use the final wish in a way that will save the future for land, sea, and all her friends?