Emily is delighted when her family returns to Brightport but their attempts to follow Neptune's orders to bring humans & merfolk together seem doomed. Thrown out of mermaid school & scorned by her old enemy Mandy Rushton Emily goes in search of the lost sirens who were banished by Neptune to a top secret undersea cavern. Only when she uncovers the sirens' true story can she put the pieces of her own life back together.