Abby, already at 12 a cheerful hostess at the fashionable inn her great-uncle runs on Earth, takes an instant dislike to Brian, the snobbish, arrogant son of wealthy off-Earth settlers. Suddenly, both children are kidnapped by a press gang and forced to do manual labor on an artificial world--a habitat--that is being built in space. Brian knows about space, but it's Abby's clear thinking and courage that enable them to escape together by stowing away on a supply ship. Abby learns that she loves Earth best, while Brian learns to consider others. Hoover firmly engages readers by adroitly creating an atmosphere of alternating indignation, anxiety, and adventure. Her characters are drawn a little too broadly--the intrepid heroine, the arrogant rich kid who learns humility, the sneering villains--but they serve the story well enough. Unfortunately, though, the technology doesn't ring quite true: there's no obvious source of light or power on the satellite, and the picture in a video connection arrives, inexplicably, before the voice. So, as science fiction, this gets a fiction 8, science 5.