The Empire Duology (Dietz)

In a far-distant future, the Uman Empire has spread to the stars and beyond, conquering and colonizing worlds, ruling with a benevolent - but iron - fist. The Pax Umana reigns, and all is well. But on one planet, the remnants of a violent, shape-shifting race called the Sagathis are confined, kept captive by xeno-cops, who have been bio-engineered to be able to see through their guises.

In a far-distant future, the Uman Empire has conquered and colonized worlds. Once thought invincible, its reign is now fragile as alien subjects and enemies conspire against it. On holiday in the capital city, cop Jack Cato gets a glimpse of the Emperor-and realizes what he's looking at is a supposedly dead shape- shifter. His mortal enemy is still alive and once again on the run. And the fate of the Empire - and Cato's own honor - are at stake....