Half vampire, half fairy, totally unique! Isadora is special because she is different. Her mum is a fairy and her dad is a vampire and she's a bit of both. Isadora has been invited to a sleepover, which is always fun, but this time it's even more exciting because she will be staying at her mermaid friend's house under the sea! It's so much fun spending time with her watery friends, but while she's there Isadora meets a mermaid called Emerald who doesn't seem to be having such a nice time. In the middle of the night, when everyone else is fast asleep, Emerald finally reveals to Isadora what has been troubling her. Can Isadora help Emerald sort out her problem? It's the beginning of an amazing underwater adventure!