saac is a member of the elite “operator” class, on the cusp of his Choosing and obsessed with discovering the difference between himself and “the Mind:” the AI implanted in him since birth. But the Mind has just begun its journey into the core of his self; starting from the chip at the back from his visual cortex it already twines deep into his limbic system. After he chooses to become an operator, Isaac will become a node on the net, processing data for the Mind with his extra dreamwidth, unaware of any difference between himself and it.
But there are edges to his world that make Isaac unsure what he will choose. Why are most of the people in the United Americas “vacs,” while he is an operator? If the Mind can so perfectly tune the personal mind of an operator, why do so many vacs lose themselves to first-person dreaming? And why do vacs need to be remote-controlled by operators at all? Isaac needs to experience himself as separate from the Mind. And so, with extra dreamcreds, he buys an old car that can travel off the thickways and away from the stifling pressure of the “thickspace,” where bandwidth is high and Mind’s power over his emotions is greatest. But even more important, he begins secretly microwaving the virus-laden bacteria destined to build the network of silica filaments that give the Mind read/write access to his brain, rendering them inert before he is forced to ingest them.
His parents are beside themselves as they realize he’s differentiating: if he chooses to become a vac, he and his parents will be made to gradually forget one another. As his development lags, the Mind’s movements inside him seem increasingly ham-handed, especially as he contemplates a book he found in his parent’s basement. But writing has been forgotten, replaced by a dream-language that has subsumed and altered all human knowledge. As he presses to understand the book, the AI manipulates his emotions in ways that feel alien, allowing him to differentiate himself from it. Why? Unable to read, he becomes fascinated with the idea that a system of information exists entirely outside the influence of the Mind.
But the Mind is not without its own measures. It enrolls him in a special “Vac Studies,” class, pairing him with Roman: an investigator who travels into the thinspace where the Mind’s surveillance is weaker. Roman is a charming intellectual, but one whose brutal intellect has been thoroughly colonized in exchange for the fulfillment of desire. Isaac is fascinated with his establishment-track knowledge but suspicious. Roman takes Isaac to see an operator-turned-vac, Bob, who is acting as a spy within a plot to overthrow the Mind. Isaac sees in Bob his own possible future on the other side of the thick/thinspace divide.
In school, Isaac meets Jethro, a vac-become-operator who works hard but bears the strain of conformity. Billy is Isaac’s best friend, and he doesn’t strain for anything at all. He wears his operator privilege like a nude sunbather wears the sun’s heat.
Isaac’s antagonistic approach to life is not without its interpersonal consequences: he seems unable avoid bullies. In gym, during a game of remote-control basketball (where students operate their partners) two “junior generals” execute an attack against the three of them, using the intense emotions of sports as a cover for their violence before the Mind can paralyze them.
Isaac and Billy befriend Jethro after the fight and punishment, discovering additionally a shared love of chess. But during a game, Billy’s insistent harassment of their vac waiter triggers Jethro and they fight. Isaac sides with Jethro and loses his best friend.
In the days to come, the Mind overplays its hand. Bob has a breakdown, and Roman leaves him exposed and betrayed, his life in danger. Isaac finds this fundamentally wrong. And on a deeper level, he interprets it as a threat: a threat to his possible future self. Not to be manipulated, he quits Vac Studies in a rage.
Still furious, Isaac presses out into the thinspace to find the Jaguar, who is said to be able to hack the mindscreen and liberate operators from the Mind’s neural control. In a seedy rural market, Isaac drinks drugged beer and is left unconscious—without his car—in the rain. But the Jaguar did not leave Isaac completely bereft. In his pocket, Isaac finds what he believes is a hallucinogen.
Hitchhiking back, he meets Sol. They recognize each other because, previously in the novel, Isaac had knocked on her father’s door, having heard he was a bookseller that taught reading. Sol is a brilliant teenage girl whose mother left to become an operator and whose rage-stricken father no longer sells books or teaches reading: lost to revolutionary struggle. Sol agrees to teach Isaac to read in order to learn secrets that could free her mother, should her mother someday wish to become free of the life she chose.
Back at home, Isaac’s parents have a final go at convincing him of the importance of remaining an operator, showing him first-person memories of their life. His father was a young seminarian who dropped out to pursue the moral implications of the mindchip, running consensual tests on prisoners. But Isaac remains unconvinced.
First, Sol teaches Isaac a method for controlling his emotions that will keep the Mind from surveilling him. Next, she teaches him to read using Farenheit 451 as a primer. As Sol and Isaac’s relationship develops and they argue about Fahrenheit 451 and 1984, Isaac learns a lexicon that can hold his rebellious ideas.
Predictably, Sol and Isaac fall in love. But after the first torrent of their love subsides, Isaac’s mindscreen alerts him that Sol’s life is in danger, and he operates her to save her from a black widow spider. Weeping, she is irrevocably reminded of his identity as a member of the operator class, a necromancer of unwilling bodies, and breaks off their relationship.
Isaac is alone. He’s lost Sol and Billy. His parents are furious at him. And Jethro is kind of boring. Over months, Sol won’t respond to his messages. So the night before his Choosing Isaac opts for what he believes is the third way, taking the Jaguar’s hallucinogen. Tripping, he experiences what it’s like to be the Mind.
But “choice” was always an illusion. Choice takes place in millions of micromoments, not in a glorious rush of willpower in the noon sun. So the Mind assumes control of Isaac’s body quietly and marches him off to his work assignment, his eyes flashing and going cold, his memories deleted.
In the planned sequel Isaac is an amnesiac vac when Sol finds him and attempts to restore his memories. As he recovers, he rages against the Mind and joins the revolutionary struggle, while she moves towards toward spirituality rather than bullets and blood for her freedom.