From back cover:
It is a perilous adventure to find fairyland, and before he set out, David was warned of the difficulties and dangers. But the sweet, crystal fairy music had called him and he wanted to find fairyland more than anything else in the world, so he began the journey.
There is delight as well as danger on the way for, with the fairy, Swiftwings, he rides in the pouch of a seven-league kangaroo, and on the back of Popoff, the friendly porpoise. He meets the fishes who live in Australian waters—the John Dories, Old Wives, and little sea horses. He meets, too, the lovely green-haired mermaids of the great Cavern of Coral, and learns how shells are made.
On the fairy island where Lob-lie-by-the-fire lives, another boy, Jack, joins him, and they begin the hardest part of the journey. At last, in the Antarctic snows they find the Escalator Beam—the moonbeam on which the moving crystal steps lead to fairyland. They climb the crystal stairway and find the faraway land where the music of the spheres sings beyond the stars.