While taking a holiday to recuperate from the traumatic events at home, Benny is contacted by a rich businessman named Orlean Wolvencroft, who collects early space hardware and needs professional help to locate a missing von Neumann probe. The probes were launched from Earth in the 2040s, programmed to locate inhabitable planets, reconfigure themselves to adapt to local conditions and create ready-made colonies for human settlers. However, Eagle 11-32 seems to have missed its target planet, and may therefore be in its original condition. Benny, intrigued, accepts the job offer (and hefty paycheque), and uses her expense account to travel to the colony world Peturia and hire a ship (the Satespes), a pilot (Johannsen) and a grad student (Noele Flynn).
The search turns up nothing for ten days, but Flynn eventually adjusts their model of the probe’s flight path to take further stellar disturbances into account, and when they follow the new model, they end up in a nearby star system where the proximity of large gas giants to the star has caused a great deal of gravitational turbulence. The system has already been mapped by automatic sensors, but Flynn now discovers that they missed an Earth-like planet due to the gravity distortions. Presumably the probe landed there, in which case it is no longer in its original condition after all. Benny orders Johannsen to take them down, but the ship goes out of control and crashes. Johannsen manages to send a distress call, but isn’t sure whether it got through the gravity distortions; Benny thus decides to stay by the ship and try to repair it. However, that night, the computers crash and the ship is attacked by animals with glowing eyes, who manage to claw through the ship’s metal hull. Benny, Flynn and Johannsen flee, but the animals don’t follow them -- and when they look back, they see that the ship has gone. Benny studies the marks on the ground and concludes that, bizarre as it may seem, the ship was eaten.
When dawn breaks, Flynn spots an aircar; it flies past, apparently without seeing them, but they now have evidence that there are other people on this planet somewhere. Benny suggests that they go fishing for a break from their foul-tasting emergency rations, but the fish in the river prove to be elaborately constructed robots, which run out of power when removed from the water. Benny then finds the hollowed-out shell of a dragonfly robot, and realises that the birds overhead are making metallic clattering sounds as well. She, Flynn and Johannsen are then attacked by a pack of robot wolves that tear Johannsen apart; at the last moment, however, Benny realises that they’re after the metal and plastic in his wrist computer, clothing and jewellery. She and Flynn strip down, removing everything metal and plastic from their bodies, and the wolves subsequently ignore them. Despite the personal risk, however, Benny holds onto the emergency beacon, which she keeps securely wrapped in a towel.
Benny and Flynn make camp on the plains, but that night, they are attacked by another pack of robot wolves; however, two hunters -- a young man named Bellamy and an older man, Beardmore -- show up and shoot the wolves, “killing” them. The suspicious Benny realises that the hunters had been watching them for some time and were using her and Flynn as bait. Nevertheless, she and Flynn accompany the hunters back to their camp, where the hunt administrator, Makins, explains that they’re hunting rogue robots from a Bantu Industries megafreighter that crashed on the planet some time ago. The manifest was lost in the crash, and the hunters thus have no idea how many robots are out there; furthermore, Beardmore claims that the robots have been adapting to the hunters’ presence and learning to avoid them. Makins orders Benny and Flynn to join the hunt in order to pay for food and shelter, but Benny has noted some holes in Makins’ explanation: just who were these robots constructed for, and why is there no physical evidence that such a large ship crashed on the planet?
Benny accompanies Beardmore on an expedition to capture a herd of “elephants” that quarry rocks rather than eating vegetation. The herd panics and stampedes when they are attacked by a wolf, but Benny manages to get through the herd to safety on the other side before the hunters start shooting. The wolf is crushed in the stampede, and when Benny examines it, she can find no power source. Flynn jokes that the carnivores get their energy from eating the herbivores; she doesn’t actually believe this is possible, but when Beardmore admits that he’s never seen robots like this before, Benny and Flynn conclude that Makins isn’t telling his hunters the truth about the robots’ origins. They also can’t help but wonder why he has supplied them with low-tech weapons. The next expedition sets off -- and is attacked by a new type of carnivore, sabre-toothed tigers that hide in the tall grass and attack the hunters. There is one tiger for each hunter; Bellamy is killed and Beardmore wounded, but Benny manages to grab Bellamy’s gun and shoot the three remaining “tigers,” saving herself, Beardmore and Flynn.
A medical team takes them back to the hunters’ spaceship, which is hovering above the ground so no animals can get to it; there, Benny and Flynn demand to know why Makins didn’t warn the hunters about the sabretooths, and he is forced to admit that the robots were designed to adapt to local conditions and reconfigure themselves. Benny realises that the sabretooths “evolved” from the wolves, and have adapted specifically to attack and kill humans. However, Makins refuses to let Flynn examine the robots’ bodies, claiming that the robots are Bantu Industries property and threatening to charge her and Benny with industrial espionage. Frustrated, Benny steals Makins’ computer pad and gives it to Flynn, who analyses its data and discovers that the robots have adapted themselves using parts from the Satespes. Since the Satespes included AI processors, it’s possible that the robots on this planet could become sentient.
Benny tries to enlist Beardmore’s help, but he doesn’t believe her claim about the evolving robots. As she and Flynn ponder their next move, they are confronted and knocked out by security guards. They awaken to find that Makins has dumped them in the fields outside along with Beardmore, who caught Makins trying to dispose of the women and ended up with them when he protested. Benny catches a robot fish so Flynn can analyse its software, and while doing so, finds the skeletal remains of an actual, living fish in the riverbed. Flynn is bewildered by the robot’s remarkably primitive source code, but when she finds the word “UNASA” in the coding, Benny realises that it stands for the United Nations Aeronautics and Space Administration -- which means that the robots are not Bantu technology after all, but products of the Eagle probe. It must have landed on this planet after all, and fulfilled its programming by creating robots programmed to evolve and adapt to local conditions.
A squad of Bantu guards arrives in the area, presumably with orders to kill the fugitives. However, a new model of herbivore robot also arrives, one that has incorporated the laser cannon from the Satespes into its body in order to blast rock free of the ground. The guards get in the robot’s way and are gunned down, and Beardmore deals with the sole survivor. The fugitives steal the guards’ aircar, and while they are planning their next move, Flynn completes her software analysis and locates the colony from which the robots originated. She also realises that Makins’ pad is compatible with 21st-century technology. Makins must have known the truth all along, which is why he supplied the hunters with low-tech weapons; otherwise, if there had been an accident, the robots would have been able to upgrade themselves with dangerous higher technology.
Benny pilots the aircar while Flynn and the injured Beardmore rest. A few hours’ flight takes them to the colony, the robots’ Garden of Eden, which consists of several prefabricated buildings, including habitation and farm domes. Small robots in the farms are tending to the crops and the reservoir; these are the earliest models of the herbivore and fish robots. Presumably, some of the robots got out and adapted to the conditions outside the colony, becoming larger and more predatory. Flynn breaks through a locked door in the heart of the colony and finds the CPU of the Eagle probe, which is still receiving data from some of the external robots. Beardmore shoots and kills three sabretooths that are attacking their aircar, but when Benny studies the bodies, she finds evidence that they’ve already been shot and patched up again; these are the sabretooths that attacked the expedition earlier, and Makins has reprogrammed them and sent them to find and kill the fugitives.
Two aircars descend on the colony, and Benny sends Flynn to safety while she and Beardmore board their aircar and try to lure the others away. One of the attackers follows them, but after a brief aerial battle, Beardmore eventually manages to shoot its pilot and the aircar crashes into the side of a mountain. He and Benny return to the colony, where they find that one of the remaining guards has been killed by a sabretooth; however, they outwit it and barricade it in the freezer. They are then captured by Makins and the surviving guard, Lendale, who shoots Beardmore in the leg; however, Beardmore has been taking painkillers for his earlier injuries, and remains stronger and more alert than Makins realises. Makins reveals that he set Benny and Flynn free in the hopes that they’d find the original colony or die trying; now that they have done so, they have outlived their usefulness. Benny offers to take Lendale to Flynn, whom she claims has hidden in the freezer; when Lendale opens it, he is attacked and killed by the sabretooth. Beardmore surprises Makins and knocks him out, and Benny shoots the sabretooth with Makins’ gun.
Flynn emerges from the CPU chamber and helps Benny to patch up Beardmore’s leg. When Benny makes a chance remark about the age of the colony, Flynn reminds her about the flight path of the Eagle probe; Benny had naturally assumed that the robots had been evolving for centuries, but in fact, the Eagle probe can only have touched down on this planet within the past couple of years. Beardmore then discovers that he’s unable to contact his fellow hunters back on the ship -- and the Eagle CPU’s monitors indicate that the ship has crashed to the planet’s surface and is under attack by the animals. Flynn theorises that the ship was “region hacked” by the animals’ software in order to make its hardware compatible with their own.
The fugitives return to the ship, with Makins as a hostage. By the time they arrive, the hunters have managed to get it back in the air again, thus giving the animals a reason to keep it intact; if they take it apart now, it will crash and destroy them all. Once aboard, Beardmore makes contact with his second-in-command, Daniels, who reports that they’ve lost most of their fuel. Makins suggests taking the ship into orbit; this will give the animals further incentive to keep the ship intact, and once back in space, they can refuel from the asteroids and raw elementary particles. As they try to join Daniels, the floor gives way beneath Benny and Makins, dropping them to a lower level. Beardmore and Flynn are forced to make their own way through the ship, and eventually join up with Daniels and the other hunters. The ship’s automated defences are attacking the humans but ignoring the robots, and they’re being triggered at random by robot badgers chewing through the wires. Wolves are on the verge of breaking into the ship’s armoury, and Beardmore realises that he’ll have to get to the bridge and order the armoury to self-destruct before the wolves can adapt the weapons into their bodies -- even though this means killing the other hunters trapped in the armoury.
Benny and Makins climb a lift shaft to the bridge, but find it being torn apart by sabretooths that have incorporated some of the ship’s technology into their bodies; some have night-vision eyes, and others have incorporated bolt guns into their bodies. Makins tricks one of the sabretooths into biting into exposed circuitry, and the electrical blast earths itself through all of the robots on the bridge, destroying them. Benny then orders the ship into orbit, but to her surprise, there is another ship waiting for them there. Orlean Wolvencroft, Mason, and a bodyguard transmat over from the other ship, and Wolvencroft’s bodyguard shoots and kills Mains. Wolvencroft learned the truth about this planet by monitoring secret Bantu memoranda, and planted a monitoring device on Benny when he hired her; her mission was only a pretext to enable him to track down this planet and take the technology for himself.
Benny shows Wolvencroft the fish bones she found earlier, and warns him that the robots wiped out the animals that were competing in the same niche, destroying the planet’s interdependent ecology. Without real animals, all plant life on the planet will eventually die out, and if the robots are taken off-world, they will do the same to every planet they reach. However, Wolvencroft is confident that the robots can be reprogrammed and domesticated, and when the hunters arrive on the bridge, he offers to buy out their contracts and add generous compensation for their losses. Beardmore is the only one who agrees with Benny about the danger; the other hunters decide to accept Wolvencroft’s offer, and when Benny, Flynn and Beardmore protest, the hunters lock them up. Infuriated by this betrayal, Beardmore breaks out of their makeshift cell and agrees to help Benny and Flynn sabotage the ships’ hyperdrives so Wolvencroft and Daniels can’t transport the robots off-world.
Flynn hacks into the transmat and sends Benny to Wolvencroft’s ship’s engine room, where she tries to activate the emergency ejection systems. Before she can finish her work, technicians arrive in the engine room to prepare the ship for departure; rather than waste time and effort herding the animals aboard his ship, Wolvencroft and Daniels have decided simply to tow the hunters’ ship out of the system. Benny sabotages her gun to create an explosion and distract the technicians, but then finds a robot spider poised over the third and final eject lever, having crossed between the two ships on a web of metal cables. Mason arrives to investigate the explosion, and the spider attacks him, recognising him as manufactured technology. Benny pulls the final lever and is expelled from the ship along with the hyperdrive, the spider and what remains of Mason; however, Beardmore and Flynn transmat her to safety aboard the hunters’ courier rocket. As they flee, their departure triggers a gravity shockwave, and as Wolvencroft’s engineers try to compensate, their ship is “region hacked” and brought down to the planet’s surface. As Benny, Beardmore and Flynn depart from the system, the ship’s hyperdrives explode, creating further gravity shockwaves. The turbulence will prevent rescue ships from entering the system for the next decade, even if Benny, Flynn or Beardmore had any intention of telling anyone what had happened here. If and until rescue arrives, Wolvencroft, Daniels and the hunters will be trapped on the planet and forced to fend for themselves.