A century ago, the human-mer treaty was established to protect the mer from the humans while they guided ships through storm-plagued waters. Now, Aila and her cousin, Persephone, act as representatives for their grandfather, King Gaspar, to the human world. The mermaids share a close bond with the Prince Jarek, but when Alia catches Persephone trying to siren him into the waters, she must work to protect her friend from her cousin...