Shy, charming, peculiar, and web-toed, Alice Riley has suffered for years at the hands of her dead mother's self-righteous family, while she hides a bevy of secret abilities. When Alice rescues a drowning child, her amazing talents are exposed. Alice can remain underwater for extraordinary periods of time, and she can locate submerged objects through some type of natural sonar ability. Her new fame/notoriety puts Alice in the national news, amidst allegations that she has somehow faked or manipulated the rescue for her own glory. Alice is trapped and desperate until three amazing older women arrive in her hometown. They are the regal and flamboyant Bonavendier sisters—dignified Lilith, acerbic Mara, and whimsical Pearl—of Sainte's Point Island, their ancestral home off the coast of Georgia. They've read Alice's story in the news and are convinced that she is their long-lost (and much younger) half sister, conceived in a reckless seduction their elderly father confessed to before he died.
Like Alice, the Bonavendier sisters have webbed toes and certain amazing abilities, though none of them have Alice's marked talent for finding things underwater. Alice is no oddity to them. They explain that—like them—she is descended from a mermaid.