This summary follows the 1968 version of the novel.
Setting: Earth & Mars, from around 3529 to 3544 A.D. (see Timeline)
Patricia Cross and her son Jommy travel to the city of Centropolis, capital of the world. The Crosses are slans, telepathic offshoots of the human race who are hated and feared by regular humans and exterminated on sight. Jommy has been entrusted with the task of assassinating Kier Gray, world dictator and persecutor of the slans. Only after Gray's death will slans be able to live normal, happy lives. To do this he will need access to a great weapon invented by his deceased father, hidden in the catacombs beneath the city. His mother has long prepared Jommy for this, since she suspects that she will not be alive to do it herself.
A group of men close in on them. They split up, his mother having already resigned herself to capture, but will do her best to allow her son to escape. Just as the authorities make their move, Jommy jumps onto the rear bumper of a passing car and is whisked away.
Unfortunately Jommy senses that the occupants of this car are John Petty, head of Gray's secret police force, and his chauffeur/bodyguard Sam Enders. Although Petty has the ability to block telepathy almost as well as a slan, Jommy senses Petty's thoughts: the police chief is a ruthless man and has decided he must kill Kathleen Layton, a young slan girl, in order to undermine Gray's authority.
Just then, the two men hear on the police radio that there is an escaped slan boy in the vicinity whose mother was just killed, and that the boy was last seen riding on a car that passed through the area. As the car screeches to a halt, Jommy jumps clear and runs while the two men fire upon him. He is hit, but manages to escape through a run-down warehouse district and into a poor housing development where some of the desperate residents try to capture him for the $10,000 reward. He eludes them and finds a hiding place. He detects a nearby mind, filled with evil plots, focused on his hiding place, but whoever it is does not give him away as the searchers pass by. This individual is revealed to be a bitter elderly woman who calls herself Granny. She knocks him semi-unconscious and pries the weakened child out of the hiding place, all the while muttering to herself incessantly about how the slan boy will make her a fortune.
The next scene introduces the reader to Kathleen Layton, a young slan girl who is a prisoner of the state, protected inside the palace by Kier Gray under the pretext that she is a study subject. On the eve of her eleventh birthday she is warned in a roundabout fashion by Davy Dinsmore, a former friend of hers, that she is scheduled to be executed the next day, explaining that Gray had agreed to his cabinet that the slan girl would be terminated when she reached the age of 11.
Terribly upset, she runs off to her room and tries to go to sleep. However, she detects the thoughts of an assassin sent to kill her. Although the man has some training in blocking telepathy, just enough leaks out to let her know that someone is afraid the execution will not be carried out and is determined to take matters into their own hands. Amply warned, she is able to evade his attack. She slips out a secret passage connecting her room to Kier Gray's office.
She comes upon the mysterious Gray as he is composing a letter. He has the most impenetrable mind she has ever encountered, but despite this barrier between the two and a great deal of fear on Kathleen's part, they seem to regard each other with respect, trust, and a certain degree of affection. She tells Gray of the attempt on her life, speculating that Petty was behind it. The dictator agrees, and explains that Petty's plan is to use Kathleen's death to discredit Gray. Now, all that Gray can do to remain in a strong position — and, indeed, alive — is to prevent Petty from killing Kathleen. Gray orders the Council to be awakened for an emergency session.
The twelve members of the Council — of which Gray is the senior member, elected into that role by his fellow members — convene late at night. John Petty already has the firm support of three other members and does all he can to make the situation seem hopeless for Gray and to swing the others by confusing the issue at hand. He attempts to portray Gray as a weak and paranoid leader unwilling to do what must be done to eliminate the slan threat. Gray points out Petty's schemes to replace him and reminds the council members that any change to the current power structure will necessitate the culling of the old political order, themselves included.
In the middle of this debate, the current situation on Earth becomes clear. The slans are winning the war despite all of humanity's efforts to wipe them out. In an attempt to strengthen their own position the government has taken strong measures during the last century or so which have been counterproductive, creating an ignorant and terrified population that is rapidly descending into desperate poverty. The slans' greater intelligence ensures their superiority in the fields of science and invention, while human scientists are demoralized and unproductive. Gray expresses his regret that not a single slan scientist has been enlisted to aid them, and laments that the great slan scientist Peter Cross was murdered three years previously by the mob-like police before Cross' talents could be harnessed by the state. The only way to win the war is to either exterminate the slans once and for all, or to negotiate with them for peace — an option that Gray increasingly favors despite opposition. And lastly, to undercut Petty's schemes Gray proclaims that Kathleen will not be executed at all, but will be kept alive as part of his continued study of slan development.
Petty then moves to vote Gray out of office. Gray admits that he has known of Petty's plot for some time and has made preparations to counter it. All the members of the Council decide to support Petty's bid for power, emboldened by the knowledge that they each have a private army to back them should their elected dictator ever defy their collective will. They plan to frame Gray for treasonous collaboration with the slans, with his decision to keep Kathleen alive as evidence. Finally left with no other option, Gray reveals that he outwitted them all by "recruiting" the head of each Councilor's army and promising them a seat on the Council. At that moment the twelve "replacements" barge into the room and assassinate their superiors. Only John Petty survives this coup, and he agrees to cooperate fully with Gray's plans.
Kathleen's eleventh birthday passes without incident. Two days later she encounters Davy in the palace halls. He apologizes for his behavior of the last few months, explaining that at his father's suggestion he turned against Kathleen to protect his own life, and since she had long ago promised never to read his mind the only way to warn her of the threat on her life was to publicly taunt her with it. She thanks him for the warning and forgives him.
Jommy awakens to find himself chained to a bed in Granny's house, out in the country on the outskirts of Centropolis. Granny threatens to turn him over to the police unless he does what she says.
Three days later they get ready to go into Centropolis. From a distance, Jommy gets his first look of the palace, Kier Gray's seat of power, although it was built by slans centuries previously. He remembers his mother telling him that although it is currently held by humans, it still contains many secret chambers, including treasure troves of technological devices and weapons that humanity thankfully remains totally unaware of. It will be six years before Jommy reaches the age of 15 — at that time he will be ready to carry out his task.
Surreptitiously slipped into town in an old cart, at Granny's insistence Jommy begins his assigned task of shoplifting in a large and lavish department store, using his telepathic powers to avoid detection. While there, he learns the news that John Petty recently executed ten traitorous Council members. Petty is distrusted and disliked among the people, while Gray is respected and admired for his unwavering strength against the slan menace.
While in the department store Jommy bumps into a man rushing past. He reads the man's mind and discovers to his complete astonishment that the man is a slan. Yet as he follows the man and continues his probing, the man proves to be a very strange slan — he seems to lack telepathic abilities though he can close off his mind better than any human.
He follows the man out onto the street, and a few blocks further on sees him enter the Air Center, where all aircraft transportation in the world is controlled. Jommy is astonished — places like this have strict security to ensure no slans get through. Jommy risks entering and is shocked when he senses that all the men around him are slans, but that they lack telepathic abilities. When asked to leave Jommy removes his hat, revealing his tendrils. Although the men express pleasant surprise and welcome at seeing a fellow slan, their minds reveal something else entirely in the split second before all telepathic contact is blocked off: hatred and murderous intent towards the "snakes," slans with tendrils.
His pursuers raise the alarm but Jommy escapes through a random door. He senses in their minds the fear that the true slans will become aware that Air Central is run by these "tendrilless" slans. He makes his way to the outside of the building, onto a window ledge. Using his strong slan hands and fingers he climbs the wall and reaches the roof, where in the descending gloom he sees a ship being launched into space from a nearby building. The conquest of space is widely considered a myth, something that never happened and is a pernicious slan lie — but obviously the tendrilless slans possess this ability.
Realizing that he must escape and get to safety, he returns to the department store where he steals a few more items to placate Granny's wrath at his tardiness. He now realizes that he will need the relative security of Granny and her house until he comes of age and decides to strike a balance with Granny — give her only enough wealth to keep her dependent on him. The rest of the money he uses for his own purposes.
For the next six years Jommy lives with Granny as his "grandson," thieving for all their needs. He educates himself as best he can from a wide variety of sources, expanding his knowledge of engineering, geography, culture, history, and the various branches of science and math. He learns that supposedly during the slan war, a hundred thousand slans infiltrated human society at every level, quietly taking over control of the world, and that the only thing that ruined this scheme was the slans' insistence of converting human babies, which apparently caused such revulsion that humanity rose up in mass protest, toppling the slans.
He also continues to cautiously observe the activities of the tendrilless slans, learning that ships come and go on a regular nightly schedule. He also builds secret tunnels beneath Granny's house to provide for escape when she finally decides to betray him.
His fifteenth birthday finally arrives and he heads for Centropolis and the Catacombs. Once in town he discovers the streets deserted and defense guns being set up. A message comes over the public address system, warning that a slan ship has been seen heading for the palace and all citizens are to flee to safety.
He enters the Catacombs. His father had hypnotically planted critical information in his mind that comes to the fore as he makes his way into the tunnels. Unfortunately, the Catacombs are rigged to alarm (to deter slans and criminals from using them) so Jommy hurries in his search. And there is a further complication — the walls of the tunnel disperse thought waves, making it difficult to detect anyone else who may be down there.
He finds his father's weapon behind a secret compartment in a section of wall, and is almost immediately forced to use it to kill two guards who stumble upon Jommy. It is a potent weapon, a small rod capable of completely incinerating anything in its path. The weapon was stored with his father's notes He leaves the tunnels, taking the weapon and notes with him.
The slan ship has come and gone, but the streets are now crowded with panicked people. Jommy overhears wild and conflicting reports on the radio — maybe the ship was destroyed, or landed at the palace with the slans now speaking with Kier Gray, or that it merely delivered a message and left.
He returns to his home and finds Granny in her usual drunken stupor. But her mind is awash with thoughts of betrayal — she has told the police about Jommy.
The scene of the story returns to the palace. Kathleen is now a beautiful young woman of 17 and is being romantically pursued by her friend Davy Dinsmore. Although she and Davy are the same age, and share a very open friendship with her routinely reading his thoughts at his insistence, such a relationship would not work — being a slan, she possess the mind of a woman of 30 and he is still just a child to her. Since her near-execution on her eleventh birthday she has helped to rear him and mold his mind, taking on a more motherly role towards him.
Kathleen is also faced with the machinations of Jem Lorry, now the most powerful man on the Council, who is determined to make her the crowning glory of his collection of sexual conquests. Lorry makes it very clear that he will stop at nothing to possess her. They are interrupted by the report that a slan ship is on its way to Centropolis. The vessel drops a message capsule in the palace grounds and a Council meeting is convened. Lorry tells Kathleen that this is the opportunity he has been waiting for, the one thing that will ensure that he can have her. In order to gain admittance to the meeting, and thereby do her best to stave off Lorry's plans, Kathleen claims to have been in telepathic contact with the ship's captain, but this is only a bluff.
In recent years a dramatic change has come over Kier Gray. Before, he admired the slans and felt that peace was possible. Now he harbors a vicious hatred of slans that rivals even Petty's. Kathleen is appalled that her protector, whom she respected and trusted, has changed so completely.
The slan message contains many (clearly false) claims intended to ease tensions between the two races. They also renounce their previous attempts at conquest and express their simple desire to be left to live in peace. Gray rejects this proposal without any consideration, saying that years ago he would have been open to this possibility but now believes all slans must die.
Lorry on the other hand proposes accepting their offer, with the provision that slans be integrated into the human population by intermarriage. Furthermore, he intends to take Kathleen as his mistress to see if such a union can produce children — theoretically, such offspring should not be slans. There are already existing accounts of such attempts in the past — no children were ever born — but Lorry insists that they not rely on hearsay and that a more modern attempt should be made. The council offers no objection, and one councilor adds that should no children come from such a marriage that it would at least prevent the long-lived slans from reproducing with one another and within 200 years their race will be no more. In other words, any peaceful agreement with the slans that the Council might approve of would still end with their complete annihilation.
But whatever method they decide to use, they will negotiate through intermediaries who will have no idea that the peace deal is a trap, so the slans' ability to read minds will be of no advantage. Kathleen, however, has heard all their plans, and Petty demands — and the Council agrees — that she must be executed at once to prevent her from relaying the information to other slans, especially those in the ship who will undoubtedly come again. Gray is clearly shocked at this, showing that for whatever reason he still needs her alive. He tells the Council that it is unnecessary to kill her, revealing that the ship was unmanned and fully automated. The ship was brought down using radio interference and will be taken in for study. Gray once again insists that he keep Kathleen alive for continued observation. When asked why she lied about being in contact with the ship's captain, she admits that she did so to oppose Lorry's machinations to possess her. Although slightly annoyed that he let his infamous womanizing interfere with Council business the other members decide to go ahead and allow Lorry to take her as a mistress.
After Kier Gray gives a brief lecture on the origin of the slans [see Characters: Samuel Lann], John Petty states that it is imperative that they be exterminated outright: no intricate traps should be laid out in the guise of peace, for such schemes could easily go wrong. In light of this, Gray rules that the match between a slan and a Councilor would be inappropriate at this time and must be forbidden. As the councilors adjourn, a disappointed Lorry approaches Kathleen and tries to pursue a more "humble" approach to winning her, stating however that if he has to settle for simply possessing her body he will do so. He then leaves.
Finally, at Kathleen's request, Gray calls Davy's father and advises him to prevent his son from pursuing a romantic relationship with the slan girl, saying that such a match would adversely affect his son's budding political career.
Jommy brings the besotted Granny, and all they money they have accumulated over the years, along with him as he escapes. He takes Granny with him — despite her betrayal, he cannot abide the thought of her being hanged as punishment for harboring him all these years. He makes his way through the series of tunnels he had created beneath their house.
Realizing his only route of escape is off-planet, he makes his way into Air Central via the roof where he boards one of the ships about to take off. He manages to launch the ship but remains in Earth's atmosphere to give him time to figure out all the controls before he ventures into space.
He suddenly senses Granny being knocked unconscious — someone else in on board. He pulls out his father's weapon just in time to prevent a tendrilless slan woman from killing him. The situation is a stand off, as the two of them cover each other with their weapons and size up their opponent. He is reluctant to kill her, as he still considers the tendrilless variety to be fellow slans and her great beauty 12 captivates him. She suggests that they both lower their weapons, and Jommy reads some of the thoughts leaked from her tight mind shield: she is apparently a newlywed and expectant mother unwilling to take needless risks. He agrees and they lower their weapons. However, she has another weapon behind her back and she chides him for believing the false story she fed him through the leak in her shield. He is forced to surrender.
The woman's name is Joanna Hillory. During their lengthy, interrogation-like conversation he tells her his life story, which she does not believe. The tendrilless slans believe he is part of the organized slan movement, and she tells him that they allowed him to escape after his "reconnaissance mission" six years previously (when he stumbled into Air Central) so they could see what the true slans would do with the information he had gathered. With his current actions they conclude that he was sent to capture one of the tendrilless' ships, the true slans having no comparable technology of their own.
The story of the slan-tendrilless conflict also becomes apparent. According to Joanna, the true slans (or "snakes" as they call them) are unwilling to tolerate any kind of slan to exist other than the "pure" breed created by Samuel Lann's mutation machine. They have been mercilessly trying to wipe out their tendrilless counterparts for centuries, so Joanna's people have to take strict precautions to protect themselves. She explains that the "snakes" are also masters of deceit so they cannot trust Jommy, regardless of whether he's telling the truth or not — he must be killed. Joanna also tells him that slans alter human babies to create more of their own kind, with many horrible failures being a byproduct of the process. She adds that she herself has seen many such mutations. All of this is a revelation to Jommy and he is deeply shocked and disillusioned.
He offers to act as a mediator between the true and tendrilless slans to find a way to peacefully cooperate. While she thinks this is a waste of time, she agrees to let her superiors decide his fate. As Joanna contacts the the tendrilless council over the radio and explains the situation, Granny awakens. Together she and Jommy overpower the tendrilless woman and regain control of the ship. When Joanna is knocked unconscious Jommy is able to briefly read in her mind that the tendrilless slans have taken elaborate measures to ensure he does not escape. Their ship is surrounded by seven battle cruisers that can track the vessel wherever it goes — they have caught him in a trap within a trap. He reassures the council that his intentions are still peaceful, but there is no response.
Some hours later, Joanna regains consciousness. A prolonged discussion follows and he again tries to persuade her of his good intentions. He has come to doubt what she has told him about the "snakes" and he resolves to verify the truth about his fellow slans himself.
Just as he figures out a way to save himself from this trap, the battle cruisers open fire.
Jommy quickly takes the ship down into the lower atmosphere. Over the radio he negotiates with the tendrilless council to release Joanna if they allow him to return to high orbit.
He swears to Joanna that when he finds the true slans he will put an end to the senseless conflict between their two races. She, on the other hand, emphasizes that the tendrilless are the true masters of Earth, limitless in number and powerful, and some day they will openly take control and enslave the human race.
He puts Joanna in another room while he rigs his father's weapon into the inside of the ship's nose cone, facing outward. He then lands the ship and lets her off as agreed. Before she leaves Joanna tells Jommy that she has come to believe his intentions are pure, and that she hopes he will do all that he has promised.
His "hostage" now released, he takes off. When the battle cruisers open fire again, he uses his father's weapon to bore through the nose of the ship, allowing the beam to drill a hole in the ground beneath a nearby river which he then flies the ship into, evading the cruisers beyond their ability to pursue. Eight miles in, he stops. He hides the ship, and he and Granny split up, arranging to meet again a year later.
During the next two years he and Granny live on a ranch out in a rural valley, purchased with the fortune they had previously amassed. Using his father's notes on controlling atomic energy, he builds a variety of machines and devices in his laboratory. He builds a special car with heavy weaponry and impregnable armor and creates a subterranean fortress in a nearby mountain.
He spends a great deal of his time traveling from city to city in his special car, searching for his fellow true slans. He learns that the power of the tendrilless slans in human society is extensive, but finds no trace of the true slans anywhere.
He finally returns to the riverbed where his ship still lies. Over a period of three months he uses the inventions based on his father's notes to repair and improve the vessel. He takes a test flight to the Moon where he encounters a heavy patrol of tendrilless slan battleships and many small but potent space mines, one of which strikes his ship and forces him to land and make repairs.
When neighbors in the area of Granny's ranch become suspicious of Jommy, he hypnotizes them using special crystals to erase their suspicions and to make their attitude towards slans neutral. He also ends up doing the same for most of the people in the valley. He also changes Granny's mind, altering her memories and inclinations, doing his best to make her into a more benign and even-tempered little old lady.
The scene returns to the palace. Over many years of reading files in Gray's desk, she has memorized lists of "secret" slan safehouses whose locations are known to the authorities and are now used to trap and capture slans. With Kathleen's 21st birthday coming up in the near future John Petty insists that she be moved out of the palace and into a more secure location. Kathleen is appalled when Gray offers no resistance to this suggestion, even though all involved know this means certain death for her.
She escapes the palace with ease, stealing a plane and traveling to a slan safehouse to the east. For two weeks she lies in wait, intending to capture the first car that comes her way.
Jommy is excited to learn that a slan girl has been reported in the area. While searching for her and avoiding the police barricades, he comes across a message from a Porgrave thought-broadcasting machine that instructs him on how to find a slan refuge hidden beneath an abandoned farmhouse nearby. As he drives up to the farmhouse he makes mental contact with Kathleen. They are both filled with wonder at finally meeting a fellow slan.
Together, they take the large hidden elevator down (bringing Jommy's car with them) and explore the long-deserted slan refuge. It is a vast underground city featuring everything such a community would ever need. Their telepathy allows the two slans get to know and grow to love each other during their brief time together.
They decide to remain there for the night to avoid the police and tendrilless slans above. Knowing that the refuge is only used as a trap that could be sprung at any moment, Jommy insists on remaining near or inside his car at all times. After a few hours of rest Kathleen leaves the safety of the car briefly to get them some food. At that moment John Petty and his men raid the refuge through a secret door inside the kitchen and he shoots her through the head, killing her.
Jommy sees her death and coldly accepts the fact that his life is going to be continually dangerous and he can form no relationships. Petty and his men fire on his car, but the armored behemoth deflects their attacks. He decides to let her murderers live and easily escapes by tunneling through the underground with his atomic beam.
Two of Petty's men are tendrilless slans who radio in detailed descriptions of Jommy to their superiors. By listening to their radio frequencies he hears that the tendrilless slans have now made him their top priority, that he must be destroyed before they can begin their open takeover of Earth. Joanna Hillory has been assigned the task of hunting him down, as she knows him better than anyone.
Four years pass. Jommy's telepathic abilities have matured and been honed to an incredible degree: he can "see" through the eyes of others as well as sense the most minute "life waves" from all living things for miles around.
The tendrilless slans strike with a gigantic fleet of ships, including a crude but effective atomic cyclotron ship that destroys his mountain fortress in an instant. They have come to kill him and capture his scientific secrets. From his laboratory beneath their ranch house, he uses his arsenal of gun turrets hidden underground throughout the valley to disable, but not destroy, the cyclotron ship.
Granny remains in the house, protected from the tendrilless slans' questioning by the hypnotic blocks that Jommy has placed on her mind. Jommy flees in his ship, and sets all that he had built in the valley to self-destruct. The invaders will never know his secrets now.
His vessel, which can now be rendered invisible through an ingenious application of his father's atomic science, confuses then outruns his pursuers. He heads for Mars, then floats nearby silently, everything turned off, waiting for a period of months for the searchers to move on. He then lands on Mars where he hypnotically overpowers a tendrilless slan at an isolated mining outpost. He learns from the helpless man that after Jommy was sighted in the refuge where Kathleen was killed, the tendrilless slans began keeping careful watch on all those known to fit his physical description to make sure Jommy does not try to assume their identity at some future date. He learns the identity of a likely candidate, Barton Corliss, who regularly comes through that area. Jommy sets up an elaborate trap and captures him, and over a period of weeks uses hypnosis to learn all he can about the man, enough for Jommy to impersonate him flawlessly. He is finally finished and sets out to replace Corliss in society when he is brought in for routine examination by the authorities.
His ship is escorted to the tendrilless city of Cimmerium, where he is scheduled for an intensive battery of tests to ensure his true identity. He is carefully watched by his escort as they enter the city, and they attempt to trip him up. But Jommy has prepared well for his task, though — his knowledge of Corliss' life is complete and accurate.
Jommy, as Corliss, reminds his escort that the restorative surgery on Mrs. Corliss is due to be finished that morning. Corliss' wife had been severely injured some weeks earlier, her head crushed in a spaceship accident, and her brain is being painstakingly reconstructed. His escort gain authorization to postpone the exam, but their suspicions are heightened even further by the convenient timing.
Brain reconstruction is a delicate operation, and the presence of a spouse or close friend is required. Using a complex array of Porgrave machines, the spouse can aid in the rebuilding of the patient's brain and mind to ensure it is done properly. Jommy is brought to the hospital to oversee the last phase of her surgery. While connected to her mind he learns that the tendrilless assault on Earth is scheduled to begin in two months. This task accomplished, the examination is forestalled as he is then ordered to be taken before Joanna Hillory. In the years since they first met, she has become the resident expert on Jommy and is responsible for having tracked him down on Earth. Knowing that he would have been unable to withstand the examination, and with the certainty of being exposed by Joanna herself, Jommy is unsure what lies ahead.
He is astounded when Joanna greets him warmly and lowers her mind shield. She explains that their encounter had given her hope for the future. Since then she has secretly been working to aid him by misdirecting and delaying the tendrilless slans' pursuit. Together, they adopt Jommy's plan to use hypnotism crystals one at a time on his escorts, to ensure he passes the examination. Then, with Joanna's help, he will return to Earth and warn Kier Gray of the tendrilless attack.
At the Bureau of Statistics, Joanna brings up Samuel Lann's ancient text diary on the 'Stics Machine. The truth about the slans' origins is finally revealed: they are but one variety of natural mutation that began plaguing the world in the mid-21st century, and are neither artificial beings nor responsible for the continued infant mutations of the present. (For more details, see the Timeline from 2000-2250.) She also uses the machine to locate a secret entrance to the palace for Jommy, and arranges to have him taken to Earth.
Backed on Earth, Jommy infiltrates the palace grounds, dominating guards through hypnosis as he goes. After being guided by a nearby Porgrave thought broadcaster, he gains entrance to a hidden passage in the base of a large fountain that leads beneath the palace. It is one of the most ancient and dangerous secret passages, and has been booby-trapped since it was first built. The walls press together, forcing him into a small elevator. By using his atomic ring he is able to destroy the restraints intended for his hands.
The elevator takes him to Gray's private office where he has a prolonged conversation with the dictator. He is astounded to learn that Gray himself is a specially augmented slan, a descendent of the "prototype" variant of the tendrilless slans, and one of the leaders of the slan race. He explains some of the more mysterious aspects of the slans' existence.
Random mutations began occurring in the human population around 2000 AD, but it wasn't until 2071 that Samuel Lann discovered the first truly beneficial mutations, whom he named "slans" after himself. Persecution of the slans, who were blamed for these mutations, was carried out with an unprecedented ferocity for 500 years. After various unsuccessful attempts to hide their true nature, some of the slan survivors began augmenting themselves to remove their tendrils and making their internal organs more human in order to avoid detection. Several varieties of slan were created during this 200-year project. Their telepathic ability was altered so that there were no tendrils, their mind-reading powers now residing inside the brain itself, although this ability was designed to remain dormant for centuries and the tendrils will eventually return.
During this "camouflaged" phase the slans contrived to secretly control the human government from within. It's known that mainstream humanity will soon die out, as the rise of natural sterility among the human population continues to rise. Gray explains that when this becomes common knowledge there will be a second vicious persecution of slans, but this time they will be prepared for it. The tendrilless slans were purposefully antagonized and made ruthless to ensure their survival during this inevitable period of turmoil. And in a few decades the tendrilless will find themselves possessing telepathic powers, and their descendants will eventually have tendrils again.
As Jommy begins to explain his father's scientific secrets, he meets other true slans who are part of Gray's organization... as well as Kathleen Layton! Her temporary death was engineered by Gray, now revealed to be her father, in order to protect her from John Petty and those like him who would never let her live. Only by letting them kill her, then resurrecting her, would her final safety be ensured. Her brain was repaired using the same technique used on Mrs. Corliss on Mars, and she was "reborn" here in the secret parts of the palace where she can live in peace and safety.