A sweet (if purposive) story by the editor of Ms. magazine, couched as a modern sequel to ""The Little Mermaid"": When the Mer-Child hears Andersen's tale, he recognizes it as his parents' story, though important details differ (e.g., his father--a mariner, not a prince--remained faithful). The Mer-Child is a lonely creature: his parents' suffering ""had made them forever grown-up, and they were now a special kind, complete unto themselves."" Rejected by the mermaids because of his mixed parentage, he wanders alone in the sea until he meets the human ""Little Girl""--also rejected, because her mother was black and her father is white--wheelchair-bound on the rocky shore while her father paints. It's the beginning of an idyllic friendship, with gifts and confidences exchanged and the Mer-Child encouraging the girl to learn to swim despite her useless legs. In time, she becomes an oceanographer and environmentalist; in old age, the two are transformed into a pair of loving swallows. The story moves slowly, driven more by its several messages than by character or more universal themes. Still, Morgan writes with appealing grace, mostly avoiding the sentimentality to which tales of yearning love are prone. Zerner's elegant pen drawings embellish an unusually attractive format featuring decorative initials and tailpieces; her daughter Amy Zerner's colorful jacket art will also attract readers.