Humanity's Commonwealth won its war with the alien Shrehari Empire seven decades ago. Starships engaged in commerce have replaced the battlecruisers, and much of that commerce flows through free ports established on what was once a disputed frontier. Yet even long after the armistice, the relationship between humans and an unfathomable, easily offended species remains tense. When someone assassinates a Shrehari trade emissary on Aquilonia Station, a human-owned free port, leaving a Commonwealth Navy officer as the sole suspect, everyone fears the worst.

An alien envoy killed by a member of the Armed Services is a case for the Commonwealth Constabulary, humanity's interstellar police force. And with galactic peace at stake, the investigation lands on the desk of Chief Superintendent Caelin Morrow.

As head of the Rim Sector's internal affairs division, Morrow is one of the most disliked cops in the Commonwealth. She investigates those in authority -- members of the police, the military, and federal government officials. It's a tough job, but Morrow and her officers are also known as the last of the incorruptibles. It makes them ideal investigators to satisfy an angry Shrehari government.

However, soon after Morrow arrives on Aquilonia to dig for the truth, she realizes something more ominous than one of the seven deadly sins is behind the alien's murder. Was his death an act of passion, or an act of politics? And what will the result of her investigation mean for the future of humanity's relations with its restive alien neighbor?