The mystery heats up as Jimmy learns his secret destiny! The mer-people know that Earth's only hope is for the daughter of the original "Little Mermaid" to fall in love with Shona and bear his eggs. What they don't all believe is that Jimmy, a 12-year-old amnesiac, is that girl. After all, Shona was the only witness to Jimmy's startling transformation into the girl of his dreams, and he's decided to let the boy make his own choices. But not everyone is willing to take that chance…because if Jimmy picks his human best friend Art, the world is doomed!

ニューヨーク、産卵のため月から帰ってきた三つ子の人魚ベンジャミン、ティルト、セツ。 しかし女性として子ども（卵）を産めるのはベンジャミンだけ。 彼（彼女：普段は小さな男の子だが、好きな人の前だと絶世の美女になる、性が変わる）が 恋したのは、おちぶれたダンサーのアート。 しかしベンジャミン＝人魚が、アート＝人間の男性に恋をすれば、大きな災いが起こるという。 物語は様々な人々の思惑、感情を孕んで、やがてその大惨事と運命の愛の結末へと向かっていく。