All Systems Red

The story is told by a SecUnit that privately thinks of itself as Murderbot. Long before the book begins, it hacked its governor module, the control system that is supposed to force obedience. Instead of going rogue in any dramatic way, it mostly uses that freedom to keep doing its job while secretly consuming huge amounts of entertainment media. During a planetary survey contract with PreservationAux, it is escorting Dr. Bharadwaj and Dr. Volescu when a hidden tunneling predator erupts from beneath a crater and attacks. The SecUnit dives in, drags Bharadwaj from the creature, gets Volescu moving despite his shock, and holds the situation together long enough for the hopper to extract them. Bharadwaj is critically injured, the SecUnit is badly damaged, and the danger proves that the planet contains threats the team was not warned about. Before emergency stasis shuts it down for repair, the SecUnit notices a suspicious abort command in the HubSystem feed, hinting that the attack may not have been simple bad luck.

After repairs, the SecUnit wakes to find the team increasingly aware that it is more than a faceless tool. When it appears without armor, everyone is uncomfortable, including the SecUnit itself. Dr. Mensah asks it to help inspect the planetary hazard report because Pin-Lee suspects something is wrong. The SecUnit confirms that key parts of the report were not merely corrupted but deliberately deleted, including warnings that might have explained the earlier attack. Soon the team also discovers that six sections of the planetary map are missing. Because they cannot tell whether this is sabotage or cheap faulty equipment, Mensah organizes a closer investigation and decides to inspect one of the blank regions directly, with the SecUnit accompanying the group because security protocol requires it to stay near clients.

The trip confirms that the problems are active and dangerous. On the way out, the hopper autopilot fails, and only Mensah's manual flying prevents a crash. At the site itself, the terrain does not explain why the area vanished from the map, but the team's scanners and hazard markers begin glitching. Arada and Ratthi nearly walk into danger because their personal maps no longer match what the SecUnit can see. The SecUnit spends much of the outing pulling people back from hidden hazards while Pin-Lee struggles to make the mapping equipment work. This shows that the data loss is not limited to old files; someone or something is disrupting systems in the field as well. When the group returns to the habitat, another crisis follows almost immediately: the nearby DeltFall survey team has gone silent, and no emergency beacon has launched. Despite the risks, Mensah organizes a rescue mission, and the SecUnit successfully argues that its combat experience makes it too valuable to leave behind.

On the way to DeltFall, conversation about bot construction and enslavement unsettles the SecUnit, exposing how badly it wants distance from human attention. The mood grows worse when communications suddenly fail, but the team votes to continue. At DeltFall they find an intact but silent camp with dead perimeter systems and no response from the habitat or its three SecUnits. The SecUnit enters first and discovers the truth: the humans have been massacred inside their own habitat. From the evidence, it concludes the killers were SecUnits acting under outside control. While clearing the camp, it notices that one corpse has been positioned as bait and uses that clue to outmaneuver two hostile units. Then another attacker ambushes it, strips part of its armor, and inserts a combat override module into the port at the back of its neck. The SecUnit kills that attacker and is saved from a second by Mensah, who uses the hopper's sonic mining drill. Once airborne, it realizes the module is already downloading commands that will turn it against PreservationAux. Because there is no safe time to remove it, it tells Mensah to kill it and, when the team hesitates, shoots itself to protect them.

The SecUnit wakes later in Medical and learns that Pin-Lee and Overse successfully removed the combat override module. That relief is brief. Gurathin has investigated its systems and reveals that its governor module was hacked long ago. He suspects it could be involved in the sabotage. Pressed to explain itself, the SecUnit admits that during an earlier assignment a governor malfunction led to the deaths of fifty-seven clients, and that it hacked its replacement governor afterward. It also proves that HubSystem is lying about immobilizing it by overriding the system and pinning Gurathin to the wall before releasing him at Mensah's request. This could have shattered the group's trust, but Mensah reframes the issue: the SecUnit has already had freedom and has repeatedly chosen to protect them anyway. She asks it to stay with them until they are safe, and promises not to report its broken governor to the company.

Once the team focuses on the larger threat, the pattern becomes clear. The SecUnit connects the suspicious abort command, the autopilot failure, the attempted software update it refused, and the altered survey package. Bharadwaj and Volescu determine that a hostile satellite download was designed to seize control of the SecUnit and use it to open their medical and security systems to attackers. Ratthi reports that DeltFall's emergency beacon was destroyed rather than launched. Pin-Lee and Gurathin confirm that HubSystem has been receiving outside commands. When a drone shows that PreservationAux's own emergency beacon has also been destroyed and another drone contact vanishes to the south, Mensah realizes waiting in the habitat is too dangerous. The team evacuates in two hoppers and hides in a jungle valley whose terrain and wildlife will interfere with scans.

In hiding, the relationship between the SecUnit and the team changes further. At Mensah's request, it retracts its helmet so the others can more easily think of it as a person trying to help. Ratthi explains that Mensah is not only a scientist but an elected administrator from Preservation Alliance, a polity where bots are citizens. That matters because the attackers may not understand how much attention Mensah's death would attract. The SecUnit has left three drones behind at the abandoned habitat, and when it returns close enough to retrieve their recordings, the team finally sees who is hunting them: a GrayCris party with armed humans, armed SecUnits, and two surviving DeltFall units now repurposed. The drone data also captures a message inviting PreservationAux to a meeting for a supposed arrangement. The SecUnit judges it a trap, but Mensah realizes the invitation reveals something important. GrayCris believes PreservationAux discovered the secret of the unmapped regions, so whatever is hidden there must explain the murders and may provide leverage.

The climax turns on that leverage. SecUnit and Mensah go to the rendezvous after scouting the GrayCris base. Mensah opens by implying that PreservationAux has evidence and understands the missing map sections. When the SecUnit walks in alone, GrayCris tries to freeze its governor module and regain control, but the attempt fails because the governor is already broken. Using that surprise, the SecUnit bluffs that it is a true rogue and offers information in exchange for being taken off-planet as supposedly destroyed inventory. To make GrayCris act, it demands proof that they have removed it from PreservationAux inventory and restarted the hacked HubSystem. Then it claims Gurathin is on the way to launch GrayCris's emergency beacon. GrayCris panics because any arriving ship would expose its operation. Blue Leader insists on taking Mensah along, which complicates the plan, but the SecUnit adapts by destroying an overridden DeltFall unit sent to escort it and then swapping armor pieces so it can impersonate that unit while Mensah pretends to be a captive.

During the next flight, Mensah draws out the truth. The unmapped regions contain buried remnants of a past civilization, and those remnants distort mapping systems. If the discovery becomes public, the planet will be locked down for archeological study, ending the illegal excavation GrayCris wants to pursue. Meanwhile, Gurathin and Pin-Lee are moving to launch the beacon for real. At the remote launch site, the deception collapses, fighting breaks out, and the remaining DeltFall SecUnit opens fire. The SecUnit realizes the group is standing far too close to the cheap emergency beacon and abandons the fight long enough to save Mensah, tackling her off the plateau and shielding her from the launch blast. Both survive but are badly injured. Gurathin and Pin-Lee recover them, and the team escapes.

Afterward, the SecUnit wakes on a company station. Ratthi tells it that Mensah has legally bought its contract, and Pin-Lee uses a court order to prevent the company from purging its memory before transfer. In effect, Mensah is trying to preserve not just the SecUnit's usefulness but its continuity as a self. She plans to take it home to Preservation as a free agent under her protection. The offer is sincere and generous, and for the first time the SecUnit is being offered safety rather than control. Yet that also makes the problem sharper: even a kind future still feels like a future chosen for it by other people. After learning more about what life on Preservation would mean, it quietly leaves during the offshift, disguises itself in stolen work clothes, and talks a cargo transport bot into taking it aboard. Before leaving, it sends Mensah a message explaining that it has to decide its own future, and signs the message with the name Murderbot.