Miles Flint and Noelle DeRicci, police detectives in Armstrong Dome on the Moon, have a problem.
They've been assigned to investigate first one, then two, then three ships arrived at the Moon under peculiar circumstances. These are quickly shown to be related to humans convicted of crimes against against alien laws, who have chosen to "disappear" rather than face their sentences.
The first contains three bodies, eviscerated in a Disty revenge killing.
The second carries five Wygnin and two human children, an eight-year-old and an infant, whom the Wygnin claim are lawfully theirs for crimes committed by their parents--but they don't have the proper warrants with them.
The third is clumsily piloted in by a woman who says she's just a tourist, a passenger on the ship when a third alien race, the Rev, stopped the ship, boarded, and removed the crew and the other passengers, while she managed to evade them.
Flint and DeRicci, in their different ways, struggle with the moral ambiguities of the most unpleasant part of their jobs as Armstrong Dome detectives: turning over humans to alien justice which often seems unjust or unduly harsh to humans. It isn't a one way arrangement; the interstellar treaties involved say that each race's law applies within its own territory, and everyone, including aliens, within that territory is subject to it.
The cases we see in this book, though, are the humans convicted by intercultural tribunals of violating the laws of non-human cultures, facing punishments that by human standards are harsh, unjust, or downright cruel. We see the agony of the parents whose children the Wygnin want to take, and the fear and anger of the lawyer who faces years of hard labor in a Rev prison colony for, in her mind, properly doing her job as a lawyer.
Armstrong Dome is a gritty, lived-in place, and the major characters as well as some of the minor ones are very nicely developed. The story moves at a good pace, and we even get some glimpses of the greater depths of the alien cultures. An interesting and worthwhile read.