The Margarets

 The only human child
living in a work colony on the Martian satellite Phobos, little
Margaret Bain has invented six imaginary companions to keep boredom and
loneliness at bay. Each an extension of her personality, they are lost
to her when she is forced to return to Earth. But they are not gone.

The time will come when Margaret, fully grown and wed, must leave this
dying world as well—this Earth so denuded by thoughtlessness and
chemistry that its only viable export is slaves. For now Margarets are
scattered throughout the galaxy. And their creator must bring her selves
home . . . or watch the human race perish.