When engineer Leo Graf arrives at a free fall station circling a mining planet to teach welding, he's in for his first shock: the genetically engineered inhabitants have an extra set of arms in place of legs. A second shock comes when the company that owns these four-armed "quaddies" decides to abandon them, and Leo must use all his ingenuity to respond to this new crisis.

Winner of the Nebula Award for Best Novel, and a Hugo Award finalist.