Salvage and Destroy

Plot

"The quarrelsome, belligerent beings of Earth already had space satellites and planetary probes. Soon they would find the Ultrons' orbital beacon. The Ultrons who controlled hundreds of civilized planets knew that Earth meant trouble--its history proved that. If the beacon transmitting data was found there'd be no end to mankind's interstellar mischief. So Lucian of the Ults took on human disguise, manned a space cruiser with tame humans, and set out on a salvage and destroy mission. The beacon must be silenced and Earth brought under control. But the problems turned out to be far more complex than any Ult computer or alien commander could ever unravel!"--Publisher's description.