Zola is excited to finally visit her grandparents in the beautiful beach-side town of Kaprisa, but it doesn't take her long to notice that there's something they aren't telling her. What they do tell her is to stay away from the water, which is hard to do when there is nowhere in town she can go without being near it.
Zola soon wishes that someone had told her about the man with shark fins who knows too much about her. She wishes that someone had told her that ignoring his invitation to join him in the sea would not be as easy as walking away. Zola finds herself dragged off to the Realm of the Sea-folk, to fulfill a promise she doesn't remember making. If she ever wants to make it home, she must escape the man with the shark fins and find a way to survive her encounters with the sea-beings who want her dead.