The Benefactors have subjugated Earth for 2000 years, but not as conquerors or kings. They are God's Heavenly Host, regarded in awe by the Catholic faithful for their power and divine wrath. Their rules are few, but absolute. Radios, for example, are strictly controlled. One rule perplexes even the most devout: You cannot learn Latin, on pain of death.

In the middle-American city of St. Lucius, June Upshaw is concerned about Hesperus, the local Benefactor. Normally, he's reclusive, but lately he's been cropping up a lot. Maybe he suspects her membership in a secret society of those who believe that the Benefactors aren't angels, but aliens. But it's almost as if Hesperus were lonely for human company—her company.

Meanwhile, the Rev. Eric Nordstrum is experiencing a crisis of faith. When he is unexpectedly passed over for cardinal, Eric's troubles become disastrous when he's turned in for his one secret vice: a Latin dictionary. On trial for his life, Eric appeals to the new cardinal, an eccentric Australian named Magnus Anders. The cardinal pardons Eric and reveals to him a frightening truth. Not only are the Benefactors alien conquerors who co-opted religion to facilitate their subjugation of Earth; they have enemies. The Romans under Julius Caesar escaped Earth and, after losing their way, built a new empire among the stars capable of wiping out the Benefactors. Latin and radios are proscribed because the Romans need only a signal in their native tongue to find Earth again. It must be soon, because the Benefactors have finally learned how to transfer their souls into human bodies, displacing the previous occupants.

Magnus recruits Eric for a mission into the nearest Restricted Zone, a vast area forbidden to Catholics. There, the cardinal's homemade radio might be able to get through to the Romans. The quest runs afoul of bloodthirsty Native Americans, but Eric still manages to send the signal that brings the Romans back to Earth. So obsessed is he with the Benefactors' betrayal and lies that he never considers whether the returning Romans might have their own agenda.

A decidedly different "What if?"

The Romans have the best PR since Albert Schweitzer. They are the ne plus ultra of empires. Even now, centuries after barbarians overran Italy, the Romans loom larger than any other race. Written boldly across their gilded breastplates are the words "What if we hadn't fallen?"

As a result, everyone interested in alternate history gets around to the Romans sooner or later. Scott MacKay, who likes his science fiction with a good dose of theo-philosophy, must have been especially tempted by the famously pious yet Machiavellian persecutors. What if their Christian opponents hadn't been a few zealots from Judea, but an army of alien energy beings from the center of the galaxy? Well, that should change things.

What's different about MacKay's Romans is that they developed technology, including cars and rockets, which advanced even further during their exile. But in an intriguing contrast, their society is stagnant, thanks to the perpetual rule of Julius Caesar's soul, kept alive by a Benefactor-made contraption.

The Benefactors' loss of perspective is perhaps the most compelling theme. Cut off from home, dispersed among Earth's burgeoning peoples, the aliens become unfocused, confused and even deluded by their own lies. Though not the first to tell of victims humanizing their conquerors, MacKay furnishes the Benefactors with resonance and even a sheen of pathetic tragedy.

Eric, the pivotal character, at first seems to be that kind of flat protagonist who tirelessly—and tiresomely—saves an entire people through sheer indomitability. But Eric is forced to evolve. When the Benefactors betray him, he turns to the Romans; but the Romans betray him too. There is a small thrill in the moment when Eric comes into his own, finally refusing to exalt any Roman or Benefactor above himself.