Having barely avoided self-destruction, an ancient race has expanded to eight other worlds. While the Beings explored Earth numerous times during two centuries with their flying saucers, they didn't consider the primitive Terrans worth contacting. That changes when their worlds came under attack from a relentless, mysterious foe. The aliens offer to repair Earth's ravaged environment in exchange for pilots and soldiers to fight their foe. The First Earth Expeditionary Force battles in space and on the ground while trying to comprehend how thousands of humans had been conscripted into fighting for the enemy. Equally puzzling for FEEF is figuring out the motives of robot-like creatures that serve the aliens, and discovering the origin of centuries old ruins on several planets and a seemingly uninhabited community under a protective dome.