Another detective novel!
Miles and Ekaterin, now married, are on their honeymoon, somewhere, when Miles gets waylaid in capacity as imperial auditor in order to investigate a possible murder, the detention of Barayaran ships and spacers, and a fraught diplomatic situation. Ekaterin, realizing this is her life now, joins the fun along with their two developing children, currently incubating in uterine replicators.
The mission brings them to “Quaddie space”. This novel ties together a 20 year old novel that Bujold wrote early in her career and won a Hugo for: Falling Free. Falling Free is a very good novel about a group of genetically engineered space workers, who have four arms (and no legs) to better allow them to work and maneuver in zero g environments (free fall) before the implementation of artificial gravity. The novel involves an earth man teaching them, realizing they have humanity, and helping them fight for their freedom. It never quite feels like it fits in the same universe until this novel.
But now, hundreds of years later Miles finds out that a group of Barayaran soldiers are charged with beating up a Quaddie woman, who they believed had murdered a shipmate. It turns out that their shipmate actually tried to defect (which is hard to do when not in war) because he is in love with the woman, a professional Quaddie dancer.
So while investigating this situation, Miles realizes there is a murder to deal with, and one that has significant galactic implications.
This novel entirely takes place in space and on stations, something that hasn’t happened for a few novels yet. In addition, spending time with Quaddies allows the series to think through the further implications of the vast amount of genetic engineering present in the series. This is a series without aliens, which can feel limiting, but the addition of genetics allows the different lifeforms to stand in for what would have otherwise been aliens.
(Photo: https://www.amazon.com/Diplomatic-Immunity-Lois-McMaster-Bujold/dp/0743435338/ref=sr_1_1?crid=1FGQGRO13HAK0&keywords=diplomatic+immunity+bujold&qid=1565002864&s=gateway&sprefix=diplomatic+immunity%2Caps%2C121&sr=8-1)