Story so far

Murderbot is a rogue SecUnit, a part-organic security construct that hacked its own governor module and has been free ever since. On a planetary survey it saved Dr. Mensah and her PreservationAux team from GrayCris, the corporation that had erased their hazard data, massacred the rival DeltFall expedition, and was illegally mining alien remnants under cover of legitimate work; Mensah bought its contract afterward and it left anyway, rather than be owned by anyone, even someone kind. Traveling alone, it fell in with ART, the enormous media-obsessed research transport that remade its body so it could pass for human and became the closest thing it had to a friend, and with ART's help it learned that the Ganaka Pit massacre of fifty-seven humans it had blamed itself for was caused by sabotage malware and not by any choice of its own. Then it smuggled itself to GrayCris's abandoned terraforming facility at Milu to gather proof that would protect Mensah, befriended Miki, the free and guileless human-form bot belonging to Don Abene's GoodNightLander Independent assessment team, and exposed the GrayCris assassins Wilken and Gerth, only to watch Miki die throwing itself at a combat bot so that Murderbot could kill it. Grieving, it faked its own death, escaped with the Milu mining logs and the assassins' hidden evidence, and decided that this time it would carry the proof to Dr. Mensah in person.

Book four opens with Murderbot riding the dim bot-piloted cargo transport it calls Ship back into HaveRatton Station, only for HaveRatton's Port Authority to divert Ship to a slot beside the station security team's deployment point. Assuming the diversion is about it, Murderbot pulls on the evac suit it escaped Milu in, cycles out the far airlock, crawls along the outside of the station, and talks a cargo bot and a docked transport into letting it walk through onto the docks, deleting itself from every log as it goes. In the station mall it buys the first set of clothes it has ever chosen for itself, packs away the armor-piercing weapon it rebuilt from Wilken and Gerth's gear, and uses ART's templates to grow its hair another two centimeters so that humans familiar with SecUnits will not recognize it. Then it watches twenty-three operatives in power suits and forty-seven drones form up to board Ship, identifies their logo as a security company called Palisade, and lifts their comm chatter off a station drone: they are hunting a rogue SecUnit. The newsfeed is worse. GrayCris has accused Dr. Mensah of corporate espionage; Arada, Overse, Bharadwaj and Volescu left for Preservation thirty cycles ago; and Mensah, who was supposed to follow them, has disappeared, with the only confirmed fact being that she is somewhere on TranRollinHyfa, the corporate hub where GrayCris and two hundred other companies keep their headquarters.

Then it watches twenty-three operatives in power suits and forty-seven drones form up to board Ship, identifies their logo as a security company called Palisade, and lifts their comm chatter off a station drone: they are hunting a rogue SecUnit. The newsfeed is worse. GrayCris has accused Dr. Mensah of corporate espionage; Arada, Overse, Bharadwaj and Volescu left for Preservation thirty cycles ago; and Mensah, who was supposed to follow them, has disappeared, with the only confirmed fact being that she is somewhere on TranRollinHyfa, the corporate hub where GrayCris and two hundred other companies keep their headquarters.

Right now Murderbot is standing in the HaveRatton mall in new clothes, the Milu memory clips still buried in its arm, working the timeline backward and trying not to panic. Mensah is not stupid, and she would never have walked into hostile corporate territory without the bond company's protection, which means she was tricked, trapped, or taken. Palisade is boarding Ship behind it, journalists cannot find Mensah, and neither Preservation nor the company will say anything useful. And Murderbot has just understood what frightened GrayCris badly enough to seize a planetary leader after months of lawsuits: Milu. Whatever has happened to her happened because Murderbot went there.