Emily - half mermaid, half human - loves life on her beautiful deserted island and spends her time with her best friend, Shona. Everything changes, however, when she finds a magical ring buried in the sand. As soon as she puts it on, she discovers that she cannot take it off again. Furthermore, Emily's discovery angers Poseidon so much that he casts a curse on her... Why is Poseidon so angry? Why is this ring so special? What will Emily find in the strange castle she sees emerging from the mist in the middle of the ocean? [Excerpt from the text on the back cover of the edition]