When a body is uncovered during construction work in Mars' Sahara Dome, it provokes a crisis in Human-Disty relations which can only be solved by finding out who died and why.
I liked that the author's aliens really are aliens, part of cultures which are logical on their own terms but which we can't really understand. However, there were lots of references to earlier events in Flint's and DeRicci's careers only some of which I recognised.