Benny receives a cryptic message from an old friend, paleobotanist Liso Fortuna, but is unsure what to make of it. However, soon afterwards, she receives another message from one of Liso’s colleagues, Piotr Valkov, who claims that Liso has gone missing from their research base, possibly after finding out something unpleasant about their employer. Piotr offers to supply Benny with false credentials so she can catch a flight from Dali Prime to Tollip’s World and investigate, but Benny is reluctant to abandon Peter yet again, as she has done so too often recently and Adrian and Jason are beginning to argue over how to raise the boy properly. Nevertheless, she asks Ms Jones to check on flights to Dali Prime just in case -- and when Ms Jones questions whether it’s appropriate for Benny to be spending so much time away from her child, the irritated Benny orders her to book a flight.
Benny thus travels to Tollip’s World under the name of Anghela Maru, along with Joseph, who has been given an intelligence downgrade in order to get past customs. The planet has recently been purchased by entrepreneur Hugo Tollip, who has named it after himself until he can think of a more appropriate name. The research base has been constructed in the midst of a hot and humid jungle, and is run like a military operation by a woman named Bleize; however, Benny’s roommate, Janny Mwesto, passes on rumours that further research is being conducted at a mysterious place called the Greenhouse. There is no indigenous animal life, and so far, the scientists believe that it was wiped out by a virus that has since burned itself out.
Benny has Joseph scan the local communications network, but then all outgoing calls are shut down and the staff are told that their contracts have been extended. When Benny contacts Piotr, he admits that he’s not sure what’s happening, but he suspects that a big discovery has been made -- possibly evidence of alien civilisation. Bleize then assembles a team of scientists, including Benny, and reveals that artificial tunnels have been found beneath the jungle’s surface. The tunnels are subject to frequent electrical pulses, and nobody’s sure what effect these pulses will have on living beings; however, the teams should have enough time to conduct a preliminary survey. Bleize chats with Benny on their way to the tunnel entrance, and warns her not to wander off into the jungle; she seems to believe that this is how they lost Liso, and also appears to be genuinely concerned for the missing woman’s welfare.
The scientists and their guards arrive at the tunnels and split up, marking their way with glowing arrows. Benny and Piotr are accompanied by a friendly guard named Ogosto, and note that the tunnel walls consist of thick root fibres and that the air is fresh, even though there’s no sign of how it’s circulating. Deep inside the tunnels, they sense the approach of a static pulse and turn back, but they’re too far from the entrance, and Ogosto, disoriented, stumbles against the wall just as the pulse rushes past. The pulse earths itself through his body, and he collapses. Benny calls for help, but Bleize and the others, who have retreated from the tunnels, will be unable to return until the pulse has dissipated. Benny orders Piotr to stay with Ogosto while she explores, as this may be her only chance to investigate Liso’s disappearance without a guard watching her every move. However, soon after Benny has gone, Ogosto revives -- and stumbles off down the tunnels, ignoring Piotr’s attempts to speak to him.
Some distance further on, Benny finds a chamber surrounded by alcoves containing skeletons of creatures similar to giant hamsters. Ogosto suddenly enters the chamber and confronts Benny, but he doesn’t appear to recognise her, and, after grunting strangely at her, he stumbles off into the tunnels again. Benny tries to follow him, but loses him in the tunnels -- and in her haste, she loses her radio and forgets to place any arrow spikes to guide her back. She wanders lost through the tunnels for some time before finding an exit, only to realise that she’s now lost in the jungle; however, while looking for a way back to the base, she stumbles across the mysterious Greenhouse. Curious, she enters, and learns to her horror that it’s a testing facility in which the native plant-life is being engineered into biological weapons, such as mould spores capable of consuming a living being from the inside out within hours.
Disgusted, Benny explores the Greenhouse further, and finds a room in which scientists are digging up a gigantic root from beneath the ground. She is then spotted and questioned by Dr Sikram, but claims that Bleize sent her out to search for the missing Ogosto. Sikram is suspicious, but Benny wins him over by telling him about the alien skeletons. Excited, he reveals that his team have found evidence that the virus that wiped out the planet’s animal life was itself wiped out by a counter-virus, and that both viruses were engineered by the planet’s trees. Sikram asks Benny to wait in his office while he inquires about Ogosto, but in fact, he’s still suspicious of her, and he contacts Bleize to check her credentials. Bleize, who knows exactly who Benny really is, orders him to keep Benny at the Greenhouse until she can be questioned
Sikram is behaving strangely when he returns, and Benny thus gives him the slip and flees back to the airlock through which she entered. By the time she gets there, however, Sikram has had it sealed, and she thus ends up trapped between the two doors. Benny tries to break out using her sonic trowel, but accidentally triggers a flash-sterilisation fail-safe that will incinerate everything inside the airlock within thirty seconds. At the last moment, however, Liso Fortuna opens the door from the outside and rescues her. By the time Sikram gets to the airlock, Benny and Liso have both gone, but then Ogosto arrives. When Bleize arrives at the Greenhouse with four guards, they find that Ogosto has killed the entire staff, stripped naked and jumped down into the pit with the exposed tree root. When Bleize confronts him, he grabs the tree root and fires an electrical blast out of his body towards Bleize and the guards. Bleize avoids the blast, and must flee when the guards unexpectedly turn on her.
Out in the jungle, Liso explains that she learned about the illegal experiments in the Greenhouse and sent Benny a disc with the evidence, hidden in the lining of the ordinary message. Liso is surprised to learn that Piotr called Benny here, as she considers him a bit creepy and was unaware that he had a crush on her; however, Benny suspects that Piotr hasn’t told her the whole truth about how he arranged to get her here. Since Liso appears safe and well, Benny asks her where she’s been for the past few days, and Liso leads Benny to a gigantic tree made up of thousands of intertwined trunks. When Benny rests her hand against the tree, her mind is drawn into a communal vision of the planet’s idyllic, pastoral past. There, she meets the spokesperson for the native “hammies”, Morweningart, who explains that her people had developed a symbiotic relationship with the Trees of Life in which both species shared genetic information. When the hammies’ only natural predators, a vicious ape-like species, began to encroach on their territory, the hammies arranged for the Trees to create a virus that would limit their numbers -- but the virus went too far and sterilised every form of animal life on the planet. The Trees grew extra brain tissue to store the hammies’ minds until the virus could be neutralised, but the Trees are slow thinkers and never got around to waking the hammies up.
Benny realises that the static pulses in the tunnels were caused by a Tree transmitting a hammie’s mental energy through its roots. Morweningart confirms that Ogosto has been possessed by the mind of a malcontent named Assapartemya. Assapartemya blames the hammie community for taking too long to come to a consensus during the virus disaster, and instead of resting quietly in his Tree, he remained partly active and convinced the Tree to experiment with modulating its bio-electrical fields. The original Assapartemya is still inside his Tree, but a copy of his mind has taken control of Ogosto’s body. Benny demands that they question Assapartemya to find out what his copy is up to, but Morweningart explains that her people regard the stored mind and its copy as two different individuals and will not use force to make one explain the actions of the other.
Frustrated, Benny emerges from the Tree into her own body, where she explains the situation to Liso. Liso explains that she found the Tree some days ago and has been communicating with Morweningart ever since; she trusts the hammie completely, but Benny is more sceptical, and decides to return to the base, find out what Assapartemya is up to, and try to send a message to Braxiatel about the Greenhouse. Back at the base, she and Liso fetch Joseph and retreat to Liso’s rooms, only to find that Piotr has broken in, looking for evidence that could help him locate the missing women. In his own socially inept way, he has feelings for Liso; however, when Benny demands to know how he got together the resources to set up her fake ID and get her here, he’s forced to admit that it was actually Bleize’s idea. Aware that Liso had contacted Benny, but unsure how much she knew, Bleize used Piotr to lure Benny here so she could keep an eye on her.
Joseph, who has been monitoring internal communications, reveals that Hugo Tollip himself has arrived to investigate the discovery of the hammie skeletons -- and that contact with the Greenhouse has been lost. Benny still doesn’t know the full extent of the Greenhouse’s work, but Liso reveals that she’s made a back-up copy of the disc that she’d sent to Benny. She and Benny take Joseph and the reluctant Piotr in search of a computer with an active disc reader, but just as they find one and insert the disc into the computer, Tollip himself catches them and places them under arrest for industrial espionage. He offers to make a deal with Benny on condition that she tell him what’s happened to Bleize, and claims that he’s ready to listen to reason; he fully intends to exploit the Trees’ abilities to produce drugs and engineer DNA, but he’s prepared to accept a loss on his investment if Benny and Liso can convince him that there’s a good reason.
Before Tollip and Benny can come to an agreement, the follow-up team arrives from the Greenhouse, and Tollip has Benny and her allies locked up while he questions the guards. Joseph has remained hidden in Benny’s backpack, however, and Benny sends him through the air ducts to eavesdrop on the guards’ report. It is interrupted when Ogosto walks into the base, naked and accompanied by three of Bleize’s guards -- who use their tranq guns to take down Tollip’s guards before they can react. Ogosto, or rather Assapartemya, announces that he intends to punish Tollip for trying to impose his will on this world rather than living in harmony with it. Tollip believes that Ogosto and the guards have gone mad, but has little choice but to co-operate. The possessed guards close down the facility, overpowering the human guards and locking up the scientific staff. Joseph returns and reports the situation to Benny -- and, in passing, reveals that he downloaded the information about the Greenhouse while the disc was in the computer’s reader.
Benny, Liso and Piotr try to trick their guard, Edwards, and escape; they fail, but Bleize then arrives, explains the situation to Edwards and releases them, as she needs all the help she can get to fight Ogosto. She explains that she escaped from the possessed guards and returned to the base on foot, and Benny in turn explains what she’s learned about the hammies and Assapartemya. However, she doesn’t know the identity of the hammies possessing the other guards, or why Assapartemya has suddenly decided to keep the base’s staff alive after slaughtering the humans at the Greenhouse. Bleize insists that they deal with this matter without outside help, as she doesn’t want word of the Greenhouse to get out, and suggests that they try to convince Morweningart to question the original Assapartemya now that his copy has started killing people. Benny thus agrees to return to the Tree of Life with Liso, Piotr and Joseph, while Bleize remains in the base and tries to rescue Tollip.
One of Assapartemya’s guards spots them trying to escape and shoots Edwards with his tranq gun; however, Bleize gets clear, and Benny and her friends get to the roof and escape to safety in one of the base’s flyers. On their way to the Tree of Life, Joseph explains that the scientists at the Greenhouse had been studying the Trees and had learned that they had the ability to re-engineer DNA and pass it between different species. This is how the hammies and Trees lived symbiotically, and how the Trees developed the virus that accidentally wiped out all animal life on the planet. Tollip’s scientists believe that the retroviruses produced by the Trees could be used to repair human beings’ telomeres, thus granting them immortality -- and Tollip now plans to uproot an entire Tree and take it off-world for further study. Presumably his people have precautions to prevent the Tree from getting out of control, but at best, this could mean the death of every hammie mind stored in the Tree -- and at worst, the Tree could take offence and develop a virus capable of wiping out humanity.
Benny and her friends arrive at the Tree of Life, only to find one of Assapartemya’s guards already there. They evade him, but realise that in order to get there first he must have been sent there directly from the Greenhouse, which means he was sent for some other reason than to catch them. However, this means that the Greenhouse is unguarded, and Liso is able to contact Morweningart through the exposed root and explain the situation. Morweningart is appalled when Benny reveals what Tollip intends to do, and although Morweningart accepts that the copy of Assapartemya poses a threat to the humans, she is now unsure whether to fight him or help him. Assapartemya then contacts Benny and threatens to start killing his hostages unless she returns, but when Morweningart reveals that the guards are possessed, not by other hammies, but by other copies of Assapartemya’s mind, Benny realises why he hasn’t yet killed the staff of the research base -- and what he intends to do with them instead.
Bleize makes her way to the control room and manages to tranquillise Ogosto, but another of the possessed guards threatens to kill Tollip, thus forcing her to surrender. The guard, also possessed by a copy of Assapartemya, explains that he has realised Tollip will never give up his hold on this world; thus, instead of simply driving the humans away, he intends to place copies of his mind in all of their bodies and take the war out to the rest of humanity. Tollip has little choice but to play along and summon reinforcements, whom Assapartemya intends to possess upon their arrival; however, if Tollip gets the chance, he has a way to deal somewhat drastically with his enemy. Once the Ogosto-Assapartemya recovers, however, he forces Tollip and Bleize out of the base, along with the rest of the staff, and forces them to dig up a root from the Trees of Life. As they dig, Benny returns, accompanied by Morweningart in Liso’s body. Morweningart is appalled by what Assapartemya is doing, but he insists that his people need a strong leader who will make quick decisions, rather than the slow debate that led to their extinction during the last crisis. Morweningart accuses him of bullying and imposing his own will on others, but Assapartemya shoots her with a tranquilliser dart.
Before Assapartemya can force Benny and Piotr into the pit, another static pulse arrives along the Tree root. Bleize pulls herself out of the pit just in time, but the rest of the base’s staff, including Tollip, are struck by the pulse -- and possessed, not by copies of Assapartemya, but of Benny. The Bennys leap out of the pit and overpower their guards; only Ogosto, who has been in a human body longer than the others, is able to escape, taking the Benny-possessed Tollip as a hostage. Benny explains to Bleize that, once she and Morweningart worked out what Assapartemya was doing, they tried to stop the Tree from sending out its pulse; they failed, as the Tree was such a slow thinker, but Morweningart managed to copy Benny’s mind into the pulse instead of Assapartemya’s.
Inside the base, where Tollip’s mind is struggling with the copy of Benny’s for control of his body. Their two minds manage to communicate, and Tollip claims that he can blanket the base with a sonic blast that will stun Assapartemya long enough for the others to get inside. Assapartemya orders Benny/Tollip to send for reinforcements, but she lies, claiming that she needs to unlock the communications console first; in fact, she allows Tollip to punch in the code that will unleash the sonic blast. But as he does so, his concentration slips, and she catches a glimpse of his thoughts; he is in fact planning to wipe the slate clean by unleashing the deadly mould spores from the Greenhouse and destroying all human life on the planet (except him, since he’s already taken an antidote). Benny’s mind struggles to prevent Tollip from entering the final code, and holds him off just long enough for the original Benny and her friends to arrive. While Assapartemya is distracted, Tollip-Benny lunges at him, and Assapartemya, knowing that he’s lost, shoots Tollip and then himself -- thus killing Ogosto and the copy of Benny in Tollip’s body.
In the aftermath, Morweningart helps Benny to draw all of the copies of her mind out of the base’s staff and back into her own body; however, the copies have changed slightly in the time they spent separate, and this means Benny must learn to reconcile 80 conflicting sets of memories and personality traits. She and Bleize strike a deal; Benny will keep quiet about the illegal bio-weapons research, and in exchange, Bleize will keep the hammies’ existence a secret and claim that Ogosto went mad and killed Tollip. However, Benny fears that not all of the base’s staff will keep silent about the events here. The hammies will try to restore their world to its former state now that their minds have been woken; inside the Tree, Assapartemya is not the raving lunatic that Benny knew, and he claims that this is because the copy of his mind was driven mad by being in a human body. The scientists destroy the Greenhouse and all of the research that has been conducted there, and Piotr, who still isn’t as close to Liso as he’d hoped, is startled when Janny Mwesto hits on him. Benny returns to the Collection, but there, Ms Jones again questions whether it’s proper for a single mother to spend so much time away from her son. Benny does not appreciate her opinion, and the friendship she’d developed with Ms Jones since the Occupation finds itself on shaky ground.