Meanwhile Orlando Gardiner, the ill teenager in America, is hot in pursuit of the golden city that he saw while online, so much so that his friend Fredericks begins to worry about him. Orlando has always been odd—he has a fascination with death-experience simulations that Fredericks can't understand—but even so this seems excessive. When Orlando announces they are going to the famous hacker-node known as TreeHouse, Fredericks' worst fears are confirmed.
TreeHouse is the last preserve of everything anarchic about the net, a place where no rules dictate what people can do or how they must appear. But although Orlando finds TreeHouse fascinating, and discovers some unlikely allies in the form of a group of hacker children named the Wicked Tribe (whose virtual guise is a troop of tiny winged yellow monkeys) his attempts to discover the origins of the golden city vision arouse suspicion, and he and Fredericks are forced to flee.
Meanwhile Renie and !Xabbu, with the help of Martine Desroubins, have also come to TreeHouse, in pursuit of an old, retired hacker named Singh, Susan Van Bleeck's friend. When they find him, he tells them that he is the last of a group of specialist programmers who built the security system for a mysterious network nicknamed "Otherland," and that his companions have been dying in mysterious circumstances. He is the last one alive.
Renie, !Xabbu, Singh, and Martine decide they must break into the Otherland system to discover what secret is worth the lives of Singh's comrades and children like Renie's brother.
Paul Jonas has escaped from his World War I trench only to find himself seemingly unstuck in time and space. Largely amnesiac, he wanders into a world where a White Queen and a Red Queen are in conflict, and finds himself pursued again by the Finch and Mullet figures. With the help of a boy named Gally and a long-winded, egg-shaped bishop, Paul escapes them, but his pursuers murder Gally's children friends. A huge creature called a Jabberwock provides a diversion, and Paul and Gally dive into a river.
When they surface, the river is in a different world, a strange, almost comical version of Mars, full of monsters and English gentleman-soldiers. Paul again meets the bird-woman from his castle dream, now named Vaala, but this time she is the prisoner of a Martian overlord. With the help of mad adventurer Hurley Brummond, Paul saves the woman. She recognizes Paul, too, but does not know why. When the Finch and Mullet figures appear again, she flees. Attempting to catch up to her, Paul crashes a stolen flying ship, sending himself and Gally to what seems certain doom. After a strange dream in which he is back in the cloud-castle, menaced by Finch and Mullet in their strangest forms yet, he wakes without Gally in the midst of the Ice Age, surrounded by Neandertal hunters.
Meanwhile in South Africa, Renie and her companions are being hunted by mysterious strangers, and are forced to flee their home. With the help of Martine (whom they still know only as a voice) Renie, along with !Xabbu, her father, and Dr. Van Bleeck's assistant Jeremiah, find an old, mothballed robot-plane base in the Drakensberg Mountains. They renovate a pair of V-tanks (virtuality immersion vats) so Renie and !Xabbu can go online for an indefinite period, and prepare for their assault on Otherland.
Back on the army base in America, little Christabel is convinced to help the burned and crippled Mr. Sellars with a complex plan that is only revealed as an escape attempt when he disappears from his house, setting the whole base (including Christabel's security chief father) on alert. Christabel has cut what seems an escape hole in the base's perimeter fence (with the help of a homeless boy from outside), but only she knows that Mr. Sellars is actually hiding in a network of tunnels beneath the base, free now to continue his mysterious "task."
In the abandoned facility, under the Drakensberg Mountains, Renie and her companions enter the tanks, go online, and break into Otherland. They survive a terrifying interaction with the Other which seems to be the network's security system, in which Singh dies of a heart attack, and find that the network is so incredibly realistic that at first they cannot believe it is a virtual environment. The experience is strange in many other ways. Martine has a body for the first time, !Xabbu has been given the form of a baboon, and most importantly, they can find no way to take themselves offline again. Renie and the others discover that they are in an artificial South American country. When they reach the golden city at the heart of it, the city they have been seeking so long, they are captured, and discover that they are the prisoners of Bolivar Atasco, a man involved with the Grail Brotherhood and with the building of the Otherland network from the start.
Back in America, Orlando's friendship with Fredericks has survived the twin revelations that Orlando is dying of a rare premature-aging disease, and that Fredericks is in fact a girl. They are unexpectedly linked to Renie's hacker friend Singh by the Wicked Tribe just as Singh is opening his connection to the Grail network, and drawn through into Otherland. After their own horrifying encounter with the Other, Orlando and Fredericks also become Atasco's prisoners. But when they are brought to the great man, along with Renie's company and others, they find that it is not Atasco who has gathered them, but Mr. Sellars—revealed now as the strange blank sim who helped Renie and !Xabbu escape from Mister J's.
Sellars explains that he has lured them all here with the image of the golden city—the most discreet method he could devise, because their enemies, the Grail Brotherhood, are so unbelievably powerful and remorseless. Sellars explains that Atasco and his wife were once members of the Brotherhood, but quit when their questions about the network were not answered. Sellars then tells how he discovered that the secret Otherland network has a mysterious but undeniable connection to the illness of thousands of children like Renie's brother Stephen. Before he can explain more, the sims of Atasco and his wife go rigid and Sellars' own sim disappears.
In the real world, Jongleur's murderous minion Dread has begun his attack on the Atascos' fortified Colombian island home, and after breaking through the defenses, has killed both Atascos. He then uses his strange abilities—his "twist"—to tap into their data lines, discovers Sellars' meeting, and orders his assistant Dulcinea Anwin to take over the incoming line of one of the Atascos' guests—the online group that includes Renie and her friends—and takes on the identity of that usurped guest, leaving Dread a mystery spy in the midst of Renie and friends.
Sellars reappears in the Atascos' virtual world and begs Renie and the others to flee into the network while he tries to hide their presence. They are to look for Paul Jonas, he tells them, a mysterious virtual prisoner Sellars has helped escape from the Brotherhood. Renie and company make their way onto the river and out of the Atascos' simulation, then through an electrical blue glow into the next simworld. Panicked and overwhelmed by too much input, Martine finally reveals her secret to Renie: she is blind.
Their boat has become a giant leaf. Overhead, a dragonfly the size of a fighter jet skims into view.
Back in the mountain fortress, in the real world, Jeremiah and Renie's father Long Joseph can only watch the silent V-tanks, wonder, and wait.