Murderbot is a rogue SecUnit, a part-organic, part-machine security construct the Company built, leased out, and treated as expendable, which hacked its own governor module and has been choosing its own actions ever since. On a planetary survey it saved Dr. Ayda Mensah and her PreservationAux team from GrayCris, a corporation illegally mining alien remnants; Mensah bought its contract outright and offered it a home rather than an owner. Traveling alone, it fell in with Perihelion, the enormous, sarcastic, media-addicted university research transport it calls ART, which rebuilt its body so it could pass for an augmented human, helped it prove that the fifty-seven deaths at Ganaka Pit were caused by sabotage malware and not by its own choice, and became the closest thing it has to a friend. It exposed GrayCris at Milu; at TranRollinHyfa it fought Mensah free of a GrayCris hostage deal and nearly destroyed itself; and it went home with Mensah to Preservation Station to live as a legal refugee, where Dr. Bharadwaj began a documentary meant to convince humans that constructs are people. Then ART, invaded and seized by a hybrid alien-human intelligence, abducted Murderbot and Mensah's teenage daughter Amena and dragged them to a lost colony outside the Corporation Rim, where colonists digging into a Pre-Corporation Rim ruin had released an alien contamination that spreads through organic neural tissue and machine code alike. Murderbot freed ART, recovered its scattered crew, and made a copy of itself, Murderbot 2.0, which used Murderbot's own curated private logs to persuade a Barish-Estranza SecUnit to disable its governor module and rescue ART's captured crew; that unit now calls itself Three, and Murderbot 2.0 died trapping the alien Target Control network so Murderbot could destroy its core. Mensah arrived on a Preservation responder before corporate reinforcements could finish the job, and Murderbot, offered a trial mission with ART while keeping Preservation as its first home, said yes.
Nobody had left the system. Plan A: Get the Hell Out of Here meant decontaminating the colonists and winning Pin-Lee's legal case, built on a reconstruction of the Adamantine Explorations charter, to stop Barish-Estranza claiming them as salvage, while a second corporate explorer with more SecUnits pressed the fractured colony and the University of Mihira and New Tideland sent nothing. Murderbot went back down to the planet against everyone's agreement and killed a contaminated agricultural bot that had trapped Ratthi, Iris, and Tarik. Then the colonist Bellagaia revealed to ART's negotiator Karime that a separatist group had left for the pole nearly thirty years ago, into the terraforming engines' scan-and-comm blackout zone, and Iris, Tarik, and Ratthi flew up under cover of a bogus engine survey with Murderbot and a partition of ART loaded into an operations drone. Murderbot spotted a buried octagonal landing pad in raw camera footage, traced an equipment rail to an Adamantine cargo hatch, and led them down a tunnel into a lit Pre-Corporation Rim installation still drawing power; on the way Iris disclosed that Tarik was once in a corporate combat squad. In the dark Murderbot finally explained the thing it had been redacting out of its own account: a spontaneous false memory of the infected corpse under the Pre-Corporation Rim habitat eating its right leg had crashed it into shutdown in front of eleven humans, Three, and ART, and the humans believe it is the construct equivalent of a flashback. The installation's system, AdaCol2, made contact, learned that its counterpart AdaCol1 had been destroyed, and showed Murderbot four hundred-odd uninfected separatists whose leaders were already being worked by five Barish-Estranza personnel and a SecUnit that had slipped into the blackout zone a day ahead of them. Sheltering from a dust storm, Murderbot met Supervisor Leonide, who recognized it at once and, performing for AdaCol2's live cameras and the whole watching colony, accused the University of intending to keep the colonists here as laboratory subjects for the next outbreak. Murderbot's answer was to make media: a forty-seven-minute documentary about what a corporate contract actually does to the people who sign it, with Ratthi writing, Iris editing and narrating in a voice ART-drone stole from Bharadwaj, and Tarik giving an interview about his combat squad he did not want to give. AdaCol2 published it tagged new, and three hundred and sixty-two of four hundred and twenty-one separatists downloaded it within minutes.
Leonide's final meeting was an ambush aimed at her: a bonus-driven faction of Barish-Estranza management had revoked her codes and meant to kill her and take the colonists by force, with Iris an inconvenient witness. Murderbot broke it up, taking a projectile and shutting down the corporate SecUnit once Iris forced the manual code out of Adelsen, then fought a way out past two more hostile units, with a hacked and recovered AdaCol2 feeding it cameras and ART-drone ramming the enemy shuttle. Rather than free the corporate units outright, it seeded their archives with 2.0's governor-hacking code; a third unit, already free on that code, warned them to run and refused to come along. Leonide, patched up by Iris and admitting the mutiny was a management schism over lost bonuses, escaped with them by pseudohopper to the shuttle Ratthi had hidden under a survival tent. Murderbot crippled the pursuing corporate shuttle with two pathfinders, Tarik picked up a University ID beacon from a newly arrived baseship, and Leonide ordered her command staff and the mutineers to stand down. ART merged with its dying iteration, guessed the new arrival was Holism and said oh, joy; ART-drone shut down, Iris half-sobbed over losing a piece of Peri, and Murderbot had a large cathartic emotion.
Seven planetary days later the evacuation has begun. Holism's support ship Sum Total is lifting Bellagaia's faction off the planet with the Preservation responder escorting, and with Holism as backup and witness Barish-Estranza has had to accept Pin-Lee and Karime's documents: under the Adamantine charter the colonists own their planet and may stay or go. Its task group imploded, so it is too busy with its own wreckage to push for signatures, and the main factions are preparing to ask it to leave; Martyn calls the self-cannibalizing a symptom of an unsustainable system. Mensah, Thiago, and Karime are negotiating resettlement for the other factions in newly independent colonies outside the Corporation Rim, while Iris, Kaede, and Martyn negotiate with the separatists, who still will not leave or rejoin anyone but have committed to managing the planet as a site for studying alien remnant contamination. In four hours Mensah and Pin-Lee will sit as independent arbiters while the separatists and Holism's University representatives begin drafting that contract, which includes hard-cable comm out of the blackout zone and University repair of everything Adamantine never finished, down to hunting the contaminated ag-bots, which Murderbot considers unambiguously its job. For now the separatists are reachable only by pathfinder message packet, and AdaCol2 has requested copies of all of ART's entertainment files. Holism turns out to be another enormous machine intelligence exactly like ART; it keeps pinging Murderbot with infrastructure proposals and offers to teach it, ART keeps telling it to stop, and the two are locked in a passive-aggressive protocol contest with Murderbot and Seth as collateral damage. Murderbot handed Three off to Holism to have planetary infrastructure explained to it, after checking that Three actually wanted that rather than just saying yes. Holism's temporary station module is docked to ART while its crew and bots decontaminate and repair ART's wormhole drive.
When the drive is fixed and the contracts are signed, ART will finally be able to leave, with Holism staying behind to build infrastructure with the separatists and Mensah taking the Preservation humans home on the responder. Amena is applying to the University but has education modules to finish at FirstLanding first. Nobody has worked out what Three wants, or how to get Three to say. Ratthi and Arada are assembling a trauma recovery program for free SecUnits with Dr. Bharadwaj, built partly on the data Murderbot chose to give them about its own incident; they would like Murderbot's help and know they will not get it yet, and they are afraid to ask Three at all in case it hears a request as an order. Murderbot knows now that what it needs is trauma recovery, has asked ART for the file describing its treatment protocol, and has not yet been able to open it. It is getting there. It is still never going to like planets, and nothing in this system changed that. But it has decided, for real this time, which ship it will be on when it leaves, and it has just asked ART where they are going next.