All Systems Red

The rogue SecUnit calling itself Murderbot hacks its way onto unmanned cargo ships to travel toward the mining facility where it once malfunctioned. It hopes to learn more about the incident, of which it has little memory and which resulted in its killing 57 people. Murderbot reluctantly befriends the powerful, intrusive bot that pilots the research transport in which the SecUnit is making the final leg of its journey to RaviHyral. Murderbot allows this artificial intelligence—which it has dubbed "ART", for "Asshole Research Transport"—to make physical modifications to the SecUnit's body that will better allow it to pass for an augmented human. To gain access to the RaviHyral facility, Murderbot takes a contract as a security consultant for three scientists who are meeting with their former employer, the head and namesake of Tlacey Excavations, to negotiate the return of their research, which they believe was illegally seized by the company. Their transport craft is sabotaged, but with ART's help, Murderbot is able to land it safely. Now aware that Tlacey is actively trying to kill the scientists rather than comply with their demands, Murderbot guides them through their meeting with Tlacey, and thwarts another assassination attempt. Murderbot learns that the massacre was the result of another mining operation's sabotage attempt using malware. Tlacey's ComfortUnit—a weaponless, anatomically correct form of robot primarily used as a "sexbot"—voices its desire for freedom and willingness to help Murderbot thwart Tlacey. While the SecUnit meets with a Tlacey employee to secretly retrieve a copy of the research, Tlacey abducts one of the scientists, Tapan. Murderbot goes after her, accepting a combat override module that is intended to control the SecUnit but actually has no effect. Once inside the shuttle, Murderbot neutralizes Tlacey's guards and retrieves a wounded Tapan, and Tlacey is killed. Tapan is healed by the MedSystem on ART's ship, and Murderbot hacks the governor module of the ComfortUnit to grant it its freedom. Murderbot sets off on its own.

Murderbot makes its way to a recently abandoned GrayCris terraforming facility in orbit over the planet Milu to collect further evidence of the company's past crimes. Befriending a bot named Miki as a means to keep its presence hidden, the SecUnit secretly follows a team of humans sent to assess the facility before a new company takes possession of it. Murderbot is forced to reveal itself when the humans are attacked by a hostile combat robot, and one of the researchers is captured. Hiding its lack of a governor module and pretending to have been sent by "Security Consultant Rin", Murderbot attempts to guide the humans—most of whom have never worked with a SecUnit before—while still seeming to defer to them. The exceptions are the team's hired security detail, Wilken and Gerth, who know Murderbot's capabilities as a SecUnit and are wary of it. They divide the team, Gerth taking two of the researchers back to their fellows on the shuttle, and Wilken leading Murderbot, Miki, and Miki's mistress Don Abene to rescue the hostage, Hirune. Aware of the failings of human security professionals, Murderbot conceives its own plan to rescue Hirune, which succeeds. The injured Murderbot comes upon Wilken attempting to kill Abene, but manages to hack into Wilken's combat armor and seize control of it. Theorizing that Wilken and Gerth had been secretly hired by GrayCris to destroy the facility before anyone could discover the illegal mining activities going on there, Murderbot leads Miki and the researchers back to the shuttle. Meanwhile, Wilken and Gerth have set in motion the destruction of the tractor array that is keeping the facility from breaking up in the atmosphere. Murderbot neutralizes Gerth's combat armor and halts the destruction of the array, and the shuttle takes off just as more hostile combat robots arrive. One clings to the ship and forces its way in; Murderbot destroys it, but not before it destroys Miki. Murderbot decides to deliver the evidence to Dr. Mensah personally.

Murderbot is suspicious when the robot ship it has taken to HaveRatton Station is diverted to a dock near station security. Murderbot sneaks off the craft through a rear airlock, and soon confirms that an armed boarding team is waiting to storm the ship in search of a rogue SecUnit. Learning that Dr. Mensah has been accused of corporate espionage by GrayCris and is now missing, Murderbot determines that she has likely been abducted by the company and taken to the corporate hub at TranRollinHyfa. Murderbot realizes that its actions on Milu have put Mensah in danger, and notes the possibility that GrayCris is luring it to TranRollinHyfa, but goes anyway. Murderbot approaches the three members of Mensah's original expedition team—Ratthi, Pin-Lee, Gurathin—who are there trying to amass the funds to pay the ransom GrayCris has demanded for Mensah. They hatch a plan wherein they will pretend to have the money and arrange for an exchange, as a means to draw Mensah out of the impenetrable security zone. The ruse works, and the three researchers flee to their contracted gunship while Murderbot moves to retrieve Mensah. Murderbot dispatches Mensah's captors easily, but a station-wide alarm is triggered before they can reach a shuttle. Three hostile SecUnits arrive, and barriers close off all gates going in and out of the concourse. Murderbot convinces a human security supervisor to raise one of the barriers enough for Mensah to slip through, and seizes control of all nearby drones and hauler bots to create chaos. Murderbot puts down two adversaries, but realizes that the third is a Combat SecUnit: harder to destroy, with hacking and enhanced scanning abilities. Mensah and her team manage to manually open a gate for the critically injured Murderbot, who escapes through it. Fleeing on the gunship, they are pursued by a Palisade security ship that attacks the gunship with a computer virus intended to seize control of its systems, neutralize any augmented human crew, and open all the airlocks. Murderbot and the bot pilot hold off the worst effects of the malware, and manage to isolate the virus in a shuttle that they disengage from the gunship. With control of the gunship restored, the captain fires on the Palisade ship and the team makes their escape. Murderbot has a critical system failure, and collapses. Awakening in a med bay with Mensah and the team as they arrive at their home base, Preservation, Murderbot begins a lengthy self-repair process. Mensah and her team offer to shelter Murderbot until it is back up to 100% functionality and can decide what it wants to do next, even if it is just to watch media. The team invites Murderbot along on their upcoming expedition as their security detail, and Mensah later mentions that GoodNightLander—the contractor of Murderbot's Milu clients—also wants to hire "Security Consultant Rin". Murderbot is content to know that it has options.

Murderbot is forced to reunite with ART, who needs its help fending off an attack by a group with alien remnant technology and to find ART's missing crew.