The men were outcasts from overcrowded Earth, fleeing hopelessly from the wrath of the vindictive Empress. They had thought themselves lucky to escape in their little ship - until they realized that they had only traded a quick death on Earth for a lingering death in the black depths of space.

The planet was a gleaming sphere with two hundred million miles in diameter, floating like a jewel in the darkness. Its surface appeared to be featureless and dead, like that of so many worlds the men had passed - but there was a small hole in its side. And when the crew went to investigate the light streaming from that hole, they found a world beyond their wildest dreams. The sphere was hollow, an inverted artificial planet. At its center blazed a warm yellow sun, and around the inner surface were meadows and mountains and streams enough to support all humanity for the next million years. Suddenly the outcasts are the pioneers - and all Earth is on their debt!