This is a standalone book set in Bear's White Space universe.  I haven't read the other in this series so I can say this book stands alone quite well.

Dr. Llyn Jens works for a gigantic-bigger-than-can-be-described hospital space station.  She is what's called a rescue specialist.   She rescues sentient beings in catastrophic situations and administers medical assistance, as required. The "as required" part is what makes Llyn so unique and so good at her job; the main requirement being the ability to "think outside the box."  To assist her in helping non-human beings is a technology that enables her to add the memories of someone from that species.  When she doesn't need it anymore, she purges the identity.  What is mildly interesting is how a non-human identity can affect her in so many ways: eating, mobility, and even breathing.  But I say "mildly" because it isn't really a focus of the story; just a gizmo to allow the character to move forward.  It's been said that science fiction is really just futurism layered atop another genre; the most popular being suspense and horror, I believe.  This book is a bit different as I see it as a crime drama.

Llyn is sent to investigate a generation-ship that had been sent out at a time when humanity truly believed the Earth was in its death throes.  Since that time, AI technology blossomed and humanity (plus the rest of sentient beings in the universe) benefited from two practices:  each person has the ability to control their body functions which include, for example, levels of hormones that typically interfere with clear and logical thinking; the other is that each society can now administer a similar cleansing to a person unable to manage their own issues. It's termed "rightmindedness".  A more primitive society might term it "brainwashing".  So Llyn finds herself preparing to succor and rescue humans whom she and her contemporaries would regard as barbarians.

However, when they finally breach the ship, they find that every single crew member except for the Captain, had been placed in a cryo unit.  The Captain apparently died at his post.  They encounter a corporeal body of the ship's governing computer unit; she's called Helen.  Llyn is also there to administer to another ship; a methane-breather ship that is docked on the generation ship. But no one onboard is answering hails and it is nearly impossible for a human to safety enter such an environment even with appropriate technology.  When she does finally enter that ship she finds the whole crew asleep.  And there is no one who can answer the questions of why that ship docked with a ship that has a poisonous environment, why are the methane-breathers all unconscious, who was responsible for putting all the humans into cryo-sleep, and maybe the most important of all: how/why is the generation-ship so far from its planned course? Only some of those questions are actually relevant to the plot but all of them are involved in it.

Rescue operations are going satisfactorily; with the possible exception of Helen who initially refuses to allow anyone to help or rescue her crew.  It becomes apparent that Helen's programming is askew.  It also becomes apparent that the makeshift cryo units will probably contribute to the deaths of many of the crew; something that Llyn fears will completely unbalance Helen.  And in Llyn's eyes, Helen is yet another casualty that she has to help; whether or not Helen was responsible for what happened on her ship.

Llyn and her team transport a number of the cryo units to Core General, the hospital space station where they start to encounter weird and unpredictable system outages; which evolves into clear sabotage.  And the sabotage doesn't spare Llyn's AI shipmind, Sally, or Core General's AI, Linden.  The AIs run just about everything including access to information that might explain what's happening.  And here's where it turns into a crime drama.

Because of Llyn's specific job skills, she finds herself being relied upon to interface with just about everyone involved in order to track down the source of what they now believe is a virus.  And there's evidence that the virus can attack more than AIs, it can attack people who aren't AIs.  So, in between caring for physical patients, Llyn finds herself tracking clues throughout the space station and between species.  The more she understands about what's really going on, the more she loses her faith in her job, Core General, and herself.  And, for Llyn, those faiths are the only things that keep her going.  Having faith in or trusting other sentient beings doesn't come easily to her.  At the height of the crisis, she has an existential crisis.

The plot was just lovely.  It started us in deep space (a ridiculous term but illustrative) with the typical trappings of sci-fi, moved us into a discovery phase where we (and Llyn) start to see mysterious forces at work and tantalizing mysteries, then into an investigatory phase where Llyn (with some help she reluctantly accepts) starts to track down who is doing what and to whom.  The author takes us slowly down the path to accepting the premise that AIs are people, too.  People with foibles and weaknesses, even personality ones.  There is much made of Llyn's society's respect for non-physical beings; and a deep-seated principle that all species be accorded respect.  But although that principle colors Llyn's choices, it really isn't significant to the plot.  What is significant is the idea that AI's could become 'just people', not omniscient and all-powerful computers.  And people can make bad choices.

While I didn't really identify with a character (something endemic to hard sci-fi, maybe), it was a very interesting story that kept my attention the whole time.  I was as breathless as Llyn waiting for the next reveal of who was doing what to whom.  And I enjoyed the things the author slipped in as commentary about our current sociopathy and her utopian vision of how we might be better.  I just felt that using the AIs as the cure for our sociopathy was a bit of a cheat; maybe she just couldn't see how we'd do that on our own.  She may not be wrong…  ~~ Catherine Book

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