Elle tells her young granddaughters a story from her childhood: In the 1930s, her newspaperman uncle, Cam, takes her to Mississippi with him where he is assigned to report on a woman who is supposedly a mermaid and is selling a magical water cure. There he finds that the woman, Elizabeth, actually is a mermaid, who has sold her soul to a cruel circus magician who promised her legs. Elle is fascinated by the magician and becomes friends with Elizabeth, and eventually she and her uncle must try to save the young mermaid’s soul.