Emily Windsnap is delighted when her family returns to Brightport. But their attempts to follow Neptune's orders to bring humans and merfolk together seem hopeless.

Thrown out of mermaid school and scorned by her old enemy Mandy Rushton, Emily goes in search of the lost sirens, banished by Neptune to a top-secret undersea cavern. Can she uncover their story and reconcile her two worlds?

Join Emily in this magical adventure as she navigates challenges, faces old nemeses, and untangles a high-suspense mystery related to a group of legendary lost sirens. Will she succeed in time to save herself and her family from the wrath of Neptune?