Reality Dust
Stephen Baxter
 The plot begins not very long after the Third Expansion began (the First Expansion ended when humanity was conquered by the Squeem; the Second Expansion ended with the conquest of humanity by the Qax, and the Third Expansion, ~5400 CE, began after the events of Timelike Infinity, pursuant to Jim Bolder's destruction of the Qax home-system). The protagonist, one "Hama", an investigator for Earth's Truth Commission, is investigating the surviving Qax-collaborators (as the Qax restricted access to AS- anti-senescence technology - to collaborators, they are rather old, and are known as "Pharaohs"); he follows one renegade Pharaoh to Callisto. It is collected in the anthology Resplendent.