Murderbot is a SecUnit, a security construct of cloned human tissue and augments that the Company built and rented out, until it hacked its own governor module and began making its own choices. On a planetary survey it saved Dr. Mensah's PreservationAux team from GrayCris, a corporation hiding illegal alien-remnant salvage behind erased hazard data and a massacred rival expedition. Mensah bought its contract out of Company inventory; it walked away anyway, cleared itself of the Ganaka Pit massacre, befriended the research transport it calls ART, and stole evidence out of GrayCris's fake terraforming site at Milu. When GrayCris took Mensah hostage on TranRollinHyfa, Murderbot came back for her and tore the operation apart with Pin-Lee, Ratthi, and Gurathin, nearly destroying itself. GrayCris was exposed and besieged afterward but not necessarily finished. It now lives on Preservation Station as a legal refugee, not a citizen and not legally a person, with ART long gone and only its comm interface kept.
The book began with a body dumped in a quiet mall junction, killed elsewhere by a puncture at the base of the skull, its clothes stripped of contact DNA. The council closed the port, Mensah asked privately whether this was the GrayCris attack she has been braced for, and Murderbot took a Station Security contract under Senior Officer Indah's rules. With the free bot Tellus it named the dead man Lutran, then found the wrecked cargo hauler where he actually died, with Ratthi and Gurathin along. Special Investigator Aylen accused it, accepted its alibi, and showed it video of Lutran entering the transport alone. The cargo contract led to the outsystem ship Lalow, whose crew took Aylen and supervisor Gamila hostage until Murderbot broke in, and whose empty containers had carried ten refugees out of BreharWallHan's asteroid mines with Lutran as their contact. The refugees never left the Merchant Docks, a pressurized transfer module went missing with its records deleted, and the responder found it clamped to a bounty-catchers' vessel hiding behind the old colony ship. Murderbot crossed in an antique life-tender, seized the hostile ship's systems, got the people out alive, and was shot in the back by a refugee who recognized what it was.
The cargo contract led to the outsystem ship Lalow, whose crew took Aylen and supervisor Gamila hostage until Murderbot broke in, and whose empty containers had carried ten refugees out of BreharWallHan's asteroid mines with Lutran as their contact. The refugees never left the Merchant Docks, a pressurized transfer module went missing with its records deleted, and the responder found it clamped to a bounty-catchers' vessel hiding behind the old colony ship. Murderbot crossed in an antique life-tender, seized the hostile ship's systems, got the people out alive, and was shot in the back by a refugee who recognized what it was.
The surveillance audit it proposed never had to finish. A hover crane nearly killed it in the empty Public Docks, the summons that sent it there was spoofed off Aylen's ID, and a query about a cancelled cargo bot gave the answer: not Gamila but Balin, the Port Authority bot that asked Preservation for refuge forty-three years ago and never once requested maintenance. Under its carapace were military-grade armor and a dormant CombatBot, reactivated by BreharWallHan with old command codes. It had walked across the station's hull, entered the transport through its module lock, killed Lutran with the rods of its hatch decoder, sterilized the body so the murder would look human, and sent the corpse to the mall in a delivery cart to pull attention from the port. Murderbot fought it through Gamila's window and onto the dock floor, where JollyBaby, Tellus, and a silent crowd of station bots surrounded it, and Balin, its cover gone, shut itself down. The refugees are safe and the Lalow crew will be released, but Lutran is dead and the escape route he ran for years is severed, leaving the people still owned in those asteroids no way out. Indah has told Murderbot she was not the one who leaked its photo, that they are on the same side, and that there will be more contracts. It has said yes, but only if it is really weird.