Emily Windsnap is finally enjoying a swimmingly peaceful life on Allpoints Island, hanging out with her mermaid bff, Shona, and her new friend Aaron (half-merperson like herself). But their idyll is cut short when Emily learns that the Windsnaps and friends must return to their old home in Brightport, where construction projects are threatening a secret mermaid community under the sea. Neptune's mandate? No less than an interspecies intervention to bring merpeople and humans together, a task the imperious god feels the mixed Windsnap family is well suited for. There are just a few snags for Emily, however, like dealing with old nemeses Mandy and Mr. Beeson, figuring out her feelings toward Aaron—and untangling a high-suspense mystery related to a group of legendary lost sirens. Everyone's favorite half-mermaid is back with a splash in a sparkling new adventure her fans will be eager to get their fins on.