Corinne LaMer defeated the wicked jumbie Severine months ago, but things haven't exactly gone back to normal in her Caribbean island home. Everyone knows Corinne is half-jumbie, and many of her neighbors treat her with mistrust. When local children begin to go missing, snatched from the beach and vanishing into wells, suspicious eyes turn to Corinne. To rescue the missing children and clear her own name, Corinne goes deep into the ocean to find Mama D'Leau, the dangerous jumbie who rules the sea. But Mama D'Leau's help comes with a price. Corinne and her friends Dru, Bouki, and Malik must travel with mermaids across the ocean to the shores of Ghana to fetch a powerful object for Mama D'Leau. The only thing more perilous than Corinne's adventures across the sea is the foe that waits for her back home.

Suspicion falls on half-jumbie Corinne when local children from her Caribbean island home begin to disappear, and she is forced to go deep into the ocean to seek the help of a dangerous jumbie who rules the waves.