Eleven-year-old Miranda thinks her life is already too complicated.
Between an over-worried mom, a snobbish school rival, and an older brother who blasts salsa music to the entire neighborhood, she has enough drama to fill a lifetime of journals. But when she gets stung by a mysterious golden sea urchin in a hidden beach shop, her regular kid problems literally wash away—and are replaced by a glittering green fish tail!

Suddenly, Miranda is a real-life mermaid. Her entrepreneurial best friend, Patricia, immediately sees dollar signs and turns Miranda's medical crisis into a low-budget beachside tourist attraction. For a brief moment, Miranda is the coolest girl in school. Even her mega-crush, Joey Zelda, thinks her scales are awesome.

But the magic is spreading. Green scales are creeping up her arms, sharp fangs are replacing her teeth, and the ancient book she found warns her that she only has seven days before she becomes a sea monster forever. Can Miranda break the curse and get her regular human feet back, or will she end up as a Filet-O-Fish at the local McDonald's?