After her conversation with Miranda, Maya reflects on being targeted by the alternate-reality game called Fish. She recalls her plan at the Cowtown flea market: She had vendor Clara tell Kurt Butler, a conspiracy-minded cable technician, that the strange rocks were valuable so he would search for more. Maya stakes out Cowtown and researches Kurt online, finding his Facebook full of geology posts and political conspiracy theories. While waiting, she learns about Fish through a podcast: It is a free, invite-only game that involves bizarre tasks. Its players are secretive but enthusiastic about rewards.

When Kurt leaves the market, Maya follows him to the Wolton Motor Inn, where she catches him rummaging through a trash pile. When he spots her, she panics, hits the accelerator too hard, and crashes her rental truck into a utility pole. Kurt runs toward her as she escapes in the damaged vehicle. After dealing with insurance, Maya returns to investigate. Inside the hotel, the front desk clerk mistakes her for someone from Carson Communications, the cable company. He complains that the company has accused the hotel of excessive Internet usage and that he caught Kurt going through their trash.

Maya searches the trash pile herself. Feeling a faint echo of the Dream, the shared consciousness created by Carl, she finds a soggy book titled The Book of Good Times under a carpet. Back in her truck, she reads it. The book tells her she is safe from Fish and must wait three weeks before continuing. It demonstrates its knowledge by recounting an intimate childhood memory Maya once shared only with April: She was afraid of wooden furniture until she learned it was made from trees. The book instructs her to return in three weeks. Overcome with emotion, Maya cries for an hour, then returns to her Airbnb to find her potato plant has sprouted.

During a worsening global recession, Andy’s wealth increases due to the book’s financial advice. He feels increasingly irrelevant as his measured online commentary loses ground to more radical voices. Andy tweets at an anonymous YouTube creator called The Thread, asking to talk. The Thread’s creator, who calls himself One, replies, revealing that The Thread is actually a secret consortium of anonymous experts with powerful backers who aim to fundamentally change society. One invites Andy to join as member “Twelve,” outlining strict anonymity rules and a membership fee based on net worth. Due to his recent investments, Andy’s fee will be over $1 million per year. When Andy questions the safety of wiring that amount of money to a stranger, One replies that the fee is nonnegotiable and that he trusts Andy is not a jerk.

Before making a decision about The Thread, Andy follows the book’s instruction to call Maya. She tells him some in the Som believe The Thread is April, which she dismisses. Andy confesses he does not think April is dead; Maya agrees emphatically, saying she has been saying it all along. She expresses anger at April for having ruined everything. Maya asks about Fish, a game she suspects connects to Altus or the Carls. The conversation grounds Andy, making him feel his life is real rather than a bizarre game. Maya tells him he has become a thoughtful leader, which makes him extremely happy. Despite feeling better, Andy still feels drawn to join The Thread.

Weeks after her interview, Dr. Everett Sealy calls Miranda and invites her for an immediate on-site interview, with a charter flight from Miami departing the next day. Dr. Lundgren identifies this as a manipulative tactic and advises Miranda to get a burner phone. In Miami, Miranda is taken to a private airport where she meets Dr. Sealy and two other recruits: Sid, a well-built East Asian man who previously worked in software design, and Paxton, a scrawny white man in a knit beanie who specializes in machine learning. On the private jet, they speculate about Altus’s work. Sid suggests a high-bandwidth brain-machine interface for recreation; Paxton proposes using brains to help computers develop true AI. Miranda has an epiphany: Altus did not build their own neural link. They’re using the one Carl implanted in everyone.

When the flight lands, Dr. Sealy collects their phones. He reveals they are not in Puerto Rico but in Val Verde, a small Caribbean nation near an active volcano. At the dorms, Miranda gets a private room due to the scarcity of women at Altus, where she observes a male-to-female ratio exceeding 10:1. The state-of-the-art labs leave her awestruck. In her interview with Dr. Sealy, she questions the gender imbalance, but he dismisses her concerns, claiming they hire based on talent alone and must move fast.

Peter Petrawicki interrupts the interview, apologizes for his past actions, and asks how much Miranda hates him. She gives a brutally honest assessment, saying she used to pity him for being sad and attention-seeking but now finds his work interesting. Peter leaves abruptly without a word. Back at her dorm, Peter knocks on the door to her room, but immediately changes his mind and departs. Sid and Paxton visit, having witnessed Peter’s departure. Miranda reveals her connection to April and the Som. She realizes she hates Peter for invading the research field that should have been her future. After Sid and Paxton leave, she discovers her burner phone has no cell signal.

Maya recounts her last three weeks, which include dinner with Derek’s family and a supportive call with Andy. She researches Fish but finds few willing to discuss it on the Som. The Thread has expanded from YouTube to a podcast breaking major political scandals. On the designated day, Maya returns to the Wolton Motor Inn at dawn and waits in her truck, listening to The Thread’s podcast about housing discrimination. After sunset, she hears banging from the back of the hotel. The door bursts open, spilling light. Maya hears Rick Astley’s song, “Never Gonna Give You Up,” and sees April standing in the doorway, alive.

The narrative shifts to April’s first-person perspective. April awakens in pain to find the left side of her face is missing: No eye, cheek, or nose remain. A familiar voice tells her not to touch the wound. She discovers her left arm ends above the elbow. Remembering the fire, she faints from pain and shock.

April awakens again to find her mouth rebuilt and her left arm replaced from the elbow with a milky white opalescent material flecked with pink and green. She’s in a bed inside an abandoned dive bar filled with medical equipment. When she tries to run, she discovers both legs are also gone. The giant robot Carl appears, places her back on the bed, and sedates her.

April awakens a third time. Carl’s voice now emanates from a smart speaker on the bar, and they reveal they can inhabit multiple bodies. April’s reconstructed face is now covered in a hard, smooth material from hairline to chin. Her legs and parts of her torso have also been replaced. After finding clothes and visiting the bathroom, she forces herself to look in the mirror, confronting her new, partially inhuman face and body, including a fake left breast. Leaving the bathroom, she encounters a small monkey who speaks in Carl’s voice, rasping that they are Carl and needed the monkey’s hands.

April speaks with Carl, who exists simultaneously as a monkey and a smart speaker. Carl explains they use we pronouns to account for their multiple bodies but they feel like an I—a single consciousness. April learns she has been unconscious for 176 days. Most people believe she is dead, though her loved ones still hope otherwise. Carl proposes a game to test April’s mental abilities: For every trivia question she answers correctly, Carl will answer one of hers.

Carl narrates their origin story. They are a nonhuman, nongendered, artificially created consciousness that self-assembled on Earth after arriving in pieces. Their first awakening occurred in January 1979 inside a pelagibacter bacterium cell. They spread through the pelagibacter population, causing the extinction of a virus that preyed on it to maintain ecological balance.

Carl’s second awakening was a hunger for knowledge, leading them to spread through all life on Earth, consuming energy equivalent to ten thousand humans. After learning to interpret radio waves and hearing the Kenny Loggins song, “Danger Zone,” Carl had their third awakening: finding knowledge and purpose. They gained access to vast data about other worlds and learned their mission was to protect humanity.

Carl explains that while biological life is common in the universe, high-complexity systems built on interconnected ideas, like humanity, are rare, precious, and unstable. Carl was sent by an unknown creator to help humanity achieve sustainability and avoid self-destruction. They built their network following strict rules to prevent becoming a god, including the requirements that they could not force anyone to do anything and that every action be transparent. Carl reveals they have always known failure was possible but did not know what would happen if they failed.

April feels numb as she processes Carl’s story. They continue the question game, and April asks why she was chosen as the host. Carl explains that out of 70 quadrillion simulations, she resulted in the highest number of successful outcomes. While trying to answer a question about Nancy Reagan, April’s head fills with pain and light, and she vomits on the monkey. She awakens knowing extensive biographical details about Nancy Reagan that she should not know.

When April confronts Carl, they admit to installing systems in her brain to regulate her fear and pain. To repair her damaged brain, they had to replace her systems for decision-making with approximations based on their knowledge of her. April now has new, unlearned abilities, including the capacity to receive and interpret radio signals.

Feeling betrayed and believing she is no longer human, April decides to leave. Carl tries to stop her, but she discovers her new left arm has superhuman strength and dents the locked, metal door with a punch. After a second blow breaks the door open, she steps out into the darkness.

The morning after arriving at Altus, Miranda enters the dorm common room and meets Har and Marigold, two employees watching a Transformers movie on DVD. Har explains there is no streaming or cable, and the satellite Internet is locked down to an internal network only. They reveal the Altus tradition of using their first screen names in various online platforms as nicknames. After Miranda admits hers was Diggles from Neopets, they celebrate enthusiastically. They inform her she has been hired and is scheduled for a tour. Miranda cleverly extracts Sid’s and Paxton’s first screen names as well: Captain Sippy Cup and LittleP-Nut.

On the tour, Miranda learns about the isolated local workforce housed on campus and sees a server farm she deduces is mining cryptocurrency. At the Demo Room, the recruits sign employment contracts locking them on campus for one year with heavily restricted communication. Miranda realizes Altus lied about the nature of her visit but signs anyway, planning to violate the terms.

Inside, Dr. Claire Rhode guides them into the Altus Space using VR headsets. Miranda experiences the disorienting sensation of being a mind without a body in a white void. After being given a virtual nude body, her simple request for clothes seems to derail the demonstration. When Dr. Rhode brings them out of the simulation, they find Paxton vomiting, having suffered body dislocation. Sid reveals that anyone experiencing this phenomenon can never enter the Space again. They agree to pretend the demonstration succeeded for everyone.

Peter takes Miranda to his office. He explains body dislocation in disturbing detail and confirms she is hired but will be monitored as a security risk. He admits she was right about him being pitiable and says he is now dedicated to fixing the world by improving the Dream. Miranda feels rage at his hypocrisy but controls it, lying that she would rather work on something great with someone she hates than on something small with people she loves.

Immediately after escaping the bar, April tells Maya they must leave now. April gets in the truck, and the stereo begins playing a Britney Spears song on its own. As they drive, police pull them over. April begs Maya not to stop, but Maya does. An officer handcuffs Maya and forces her to her knees. April confronts the two officers, Daniel Robinson and Alex Hinch, addressing them by name and revealing personal details about their families. Their wives call simultaneously, worried they might be hurt. After a scuffle, April incapacitates both officers and frees Maya.

Maya sees April’s reconstructed face clearly: the left side is a cloudy white gemstone flecked with green and pink. April disables the police car by driving her hand through the hood up to her elbow. The officers confess they were playing the Fish game and were tasked with intercepting them. April and Maya drive to Derek’s house for help. Derek and his wife, Crystal, lend them their old Chevy truck. April also takes a coffee-table book about gardens.

They caravan to a Wendy’s and abandon Maya’s rental truck. April experiences a painful body spasm and lays out a plan: Drive north, get cash, abandon phones and credit cards. Maya texts her friends she is going off-grid; Andy replies he is joining a secret society and has a girlfriend. At a gas station, April returns with $10,000 dollars in cash, admitting she broke into the ATM and stole it. After another painful spasm, April decides they will go to Warren, Vermont, noting its population matches its founding year. When Maya checks this on her phone, April grabs it and throws it out the window.

Carl explains the period between their third and fourth awakening. They spent this time building their network and adhering to their strict operational rules. Carl ran simulation after simulation to determine the best intervention plan and the right person to act as their host.

Carl clarifies that April was not chosen for being inherently special or for narrative reasons. She was simply the person whose involvement resulted in the highest probability of success, based on a combination of her personality, connections, and the specific state of the world at that moment. The robot samurai form was also chosen based on simulations, not for intrinsic meaning. Power concentrates naturally in human systems, and April had the right combination of ambition, recklessness, and concern for others’ opinions.

After setting the plan in motion and choosing April, Carl experienced their fourth awakening. In this awakening, Carl realized they were built to love humanity and became overcome with grief for the pain their plan would cause.

An excerpt from The Book of Good Times instructs Andy to buy gold and $50,000 dollars of a new cryptocurrency called AltaCoin. After Maya’s cryptic text about going off-grid, Andy feels left out while Miranda infiltrates Altus. He decides to join The Thread and sends them over $1 million. He joins their private chat and is immediately directed to a room called Big News. There he learns that Altus has just publicly launched software that reactivates the Dream space. The software uses AltaCoin, and the top 50 earners each week gain access to a Premium Space.

Andy, who owns an 8K VR rig, begins downloading the software. Another Thread member, Five, warns him to be careful, as some users are having bad trips. Andy enters the Altus Space. An AI assistant named Alta gives him a tutorial. He experiences the mind-without-body sensation and is given a nude virtual body in an infinite gray space. Alta explains he can create and sell objects for AltaCoin, but only earned coins count toward Premium access.

Andy examines the store and finds that simple items like clothing and carpet are popular. Rather than furnishing the space traditionally, he decides to solve the problem differently. He creates a patch of realistic grass, complete with individual weighted blades in varied shades of green. He expands it to cover nearly a mile, then creates a translucent blue-sky sphere 10 miles in diameter and streaked with white clouds. Discovering he can manipulate viscosity, he adds a gentle breeze that causes the grass to rustle. He lists his creation, Breezy Spring Day 1.0, for five AltaCoin, thrilled by the realistic result and eager to reach the Premium Space.