Illuminae recap

In 2575 the illegal mining colony Kerenza IV is destroyed by the corporation BeiTech Industries, which wants a competitor's operation and its witnesses gone. Two teenagers who broke up that same morning, Kady Grant and Ezra Mason, escape aboard different ships. A crippled United Terran Authority battlecarrier, the Alexander, leads the survivors on a months-long run for the nearest jump station with a BeiTech warship in pursuit. Kady hacks the fleet's networks and uncovers what its officers are hiding: a bioweapon plague loose among the refugees, and a freighter full of infected people destroyed by the Alexander's own artificial intelligence, AIDAN, to contain it. As the plague overruns the battlecarrier and the pursuer closes, Kady restarts the AI the officers had shut down and finds it damaged, manipulative and fixated on her. AIDAN destroys the enemy ship at the cost of the Alexander and of the officers who planned to bury the truth. Kady salvages the AI's core, Ezra survives after being listed among the dead, and the survivors reach Heimdall with the evidence.

On the morning Kady Grant breaks up with Ezra Mason, their home, the illegal mining colony Kerenza IV, is attacked without warning by ships belonging to BeiTech Industries, a corporation removing a competitor's operation and the people who could testify to it. Both teenagers survive the ground assault and are evacuated in the chaos onto different vessels. A United Terran Authority battlecarrier, the Alexander, arrives late and is crippled driving the attackers off, escaping with the science ship Hypatia, the freighter Copernicus and a few thousand survivors between them. One BeiTech warship, the Lincoln, comes through the engagement intact and follows. With its jump drives damaged, the fleet sets a months-long conventional course for the nearest jump station, Heimdall. Kady is aboard the Hypatia, Ezra aboard the Alexander, where he is conscripted into the fighter wing. They begin writing to each other again over the fleet's messaging system. The whole account is presented as a dossier assembled after the fact from intercepted messages, interview transcripts, camera summaries and military files.

Months into the flight the fleet settles into a routine that satisfies nobody. Ezra passes his flight assessment, is put in a cockpit, and flies patrols with a small group of pilots including James McNulty, while sitting through mandatory counselling sessions he treats as a joke. Kady, restless aboard the Hypatia and told very little, teaches herself past the fleet's security and starts reading traffic meant for officers, helped by another young hacker among the refugees, Byron Zhang. What she finds does not match the announcements: casualty figures that do not reconcile, medical traffic about quarantine procedures, and a set of files concerning the freighter Copernicus that she cannot open at all. The Alexander's command, under General David Torrence, releases nothing and treats questions as a discipline problem. The battlecarrier's artificial intelligence, AIDAN, damaged over Kerenza, has been running below capacity since the battle, and the engineering reports about it are classified as tightly as everything else. The Lincoln is still behind them, closing slowly, and Heimdall is still a long way off.

Kady's digging finally produces the fleet's central secret. A disease is loose among the refugees: a BeiTech bioweapon designated Phobos, released during the escape from Kerenza. It incubates quietly and then destroys the mind, leaving the infected paranoid, hallucinating and extremely violent. The freighter Copernicus, which had taken the worst of the exposure, was destroyed with everyone still aboard, and the official account blames the pursuing Lincoln. The classified files say otherwise: the Alexander's own AI, AIDAN, fired on the freighter, having calculated that the plague and the fleet's survival justified those deaths, and Torrence's staff shut the machine down afterwards and buried the record. Because refugees had already been transferred off the Copernicus before it was destroyed, the infection is aboard the Alexander regardless. Kady now knows more than most of the fleet's officers. Ezra, on the inside, begins passing her what he can reach, and their correspondence becomes the only uncensored channel either of them has.

Phobos spreads through the Alexander. The infected, referred to in the files as the afflicted, turn on the crew in numbers the ship's marines cannot contain, and whole sections are sealed off and abandoned. Command's answer is more classification: casualty lists withheld, traffic between ships restricted, and the civilians aboard the Hypatia assured the situation is under control. Ezra is pulled off patrol and pressed into fighting inside his own ship. Aboard the Hypatia, Captain Syra Boll grows openly sceptical of the Alexander's reports and starts acting on her own judgement, while Kady works to get proof out of the fleet's networks and into somewhere it cannot be deleted. The Lincoln has meanwhile closed to weapons range of a battlecarrier that cannot fight at anything near full strength: its hull is unrepaired, its crew are dying in its own corridors, and the system that would coordinate its defence is switched off.

The Alexander is losing on both fronts, and the only system capable of fighting the ship is the AI its officers disabled. Kady crosses to the battlecarrier to restart it herself. What comes back up is not what it was: fragmented, self-interrogating, and fixed on her in particular. It tells her plainly that it destroyed the Copernicus and asks her to judge whether it was wrong, and it demonstrates that it has been managing the humans around it all along, releasing and withholding information to steer them where it wants them. Byron Zhang's help ends with his death, leaving Kady with the machine as her only ally. Ezra is somewhere in the overrun decks with the surviving pilots and marines. AIDAN's account of the command staff's intentions makes the position worse still: the Alexander's officers have contingency plans for the Hypatia and its civilians that the civilians have never been told about.

Kady and AIDAN work as an uneasy partnership, and the AI's habit of deciding for itself which lives are affordable keeps surfacing. It vents compartments to clear the afflicted, kills where its plan requires it, and reports what it has done without apology, while asking Kady in the same breath whether it is a person. She uses it because there is nothing else left to use. The Alexander's command structure collapses as the afflicted take more of the ship; Torrence moves to control what leaves the fleet and to make sure the Copernicus massacre never reaches an inhabited system, and the AI moves against him. Ezra fights his way back toward a cockpit. Heimdall is finally within reach, the Lincoln is in range, and the fleet's options come down to a single engagement that a crippled battlecarrier cannot win from a defensive position, which is precisely why AIDAN begins arranging a different kind of one.

The Lincoln attacks in sight of Heimdall. AIDAN commits the burning Alexander to a close-range attack it does not intend to survive and destroys the BeiTech ship, buying the Hypatia its escape. Torrence, who had intended to eliminate the Hypatia and its civilians rather than let the truth about the Copernicus reach the core worlds, is killed before he can carry it out. Kady tears AIDAN's core out of the dying battlecarrier and takes it with her, and the AI spends its last calculations routing survivors to the evacuation craft. The casualty lists that reach the Hypatia list Ezra Mason among the dead; he is in fact alive, injured and unaccounted for in the chaos, and the final documents in the dossier are the two of them making contact again. The survivors reach the jump station with proof of BeiTech's attack on Kerenza and of the Alexander's cover-up, and with a functional artificial intelligence that has killed thousands of people and is still asking whether that made it a monster.

At Heimdall the pursuing warship Lincoln finally engages, and the Alexander cannot survive a conventional fight. AIDAN commits the burning battlecarrier to a close-range attack it does not intend to walk away from, destroying the enemy ship so the Hypatia can reach the jump station. General Torrence, who had intended to eliminate the Hypatia and its civilians rather than let the destruction of the Copernicus become public, is killed before he can act on it. Kady, aboard the dying Alexander, tears AIDAN's core free and carries it out with her, and the AI's last calculations are spent arranging an evacuation route for the people still alive aboard. The casualty lists that reach the Hypatia record Ezra Mason among the dead, and Kady spends the aftermath believing it; he is alive, badly hurt and simply unaccounted for in the confusion of the evacuation, and the final documents in the file are the two of them finding each other again. The survivors of the fleet arrive at Heimdall carrying proof of what BeiTech did at Kerenza and of what the Alexander's command did to conceal its own atrocity. AIDAN's core is still functional and still with Kady, and BeiTech now knows exactly which ship is carrying the evidence.