Published in 2020, Hank Green’s science fiction novel A Beautifully Foolish Endeavor provides the conclusion to the two-part series known as The Carls Duology. Green’s debut novel, An Absolutely Remarkable Thing (2018), is the first book in the series. Green is a prominent Internet creator and science educator known for co-creating the popular YouTube channels Vlogbrothers, Crash Course, and SciShow with his brother, author John Green. This background directly informs the novel’s focus on Internet culture, fame, and the societal impact of technology. Like its predecessor, A Beautifully Foolish Endeavor became a New York Times bestseller and was nominated for a Goodreads Choice Award for Science Fiction.

The story begins months after the mysterious disappearance of the alien Carls and the presumed death of their viral spokesperson, April May. April’s friends—Maya, Andy, and Miranda—struggle to navigate a world grappling with loss and uncertainty until a series of bizarre clues suggests April might still be alive. Their search for answers uncovers a menacing new corporate entity, Altus, which seeks to control human consciousness. Thematically, the novel explores The Dangers of Centralized Power, The Use of Technology to Manipulate Belief and Behavior, and The Performance of Identity in the Age of Social Media.

This guide refers to the 2021 Dutton trade paperback edition.

Content Warning: The source material and study guide feature depictions of graphic violence, illness or death, racism, physical abuse, and cursing.

Plot Summary

April May addresses the reader, admitting she has been lying by omission to make people feel safe. She explains that she and her friends will now tell the full story of the events following her presumed death in a warehouse fire, which was actually an attempted murder by terrorists. She reveals the central truth: Humanity is not safe.

The narrative shifts to several months after April’s disappearance. April’s ex-girlfriend, Maya, refuses to believe April is dead. Estranged from her wealthy parents over her refusal to move on, Maya spends her time on the Som, a social media platform for solving mysteries, searching for clues. She identifies a pattern of strange events on the East Coast: lab break-ins, mysterious Internet outages, and pods of dolphins repeatedly swimming up the Delaware River to die. After an argument with her parents, Maya drives to New Jersey to investigate.

Meanwhile, April’s best friend, Andy Skampt, now a famous public figure, receives a text from April’s phone that says, “Knock Knock.” Outside his apartment, he finds a mysterious book titled The Book of Good Times. The book speaks directly to him, revealing intimate knowledge of his thoughts and confirming that April is alive but recovering. Following the book’s instructions leads him to a sandwich artist named Bex. Prompted by the book, Andy asks to go to the theater with him, sparking a connection. The book then gives him two more instructions: Begin a series of stock investments, starting with a company called IGRI, and tell his friend Miranda Beckwith that “she has to do it” when she calls.

The story moves to Miranda, a PhD student at the University of California, Berkeley. She reads a magazine profile on Peter Petrawicki (PP), April’s antagonist, who is building a secret, billion-dollar research project in Puerto Rico called Altus. Based on the scientific fields involved, Miranda, whose own research is in brain-computer interfaces, deduces that Altus is developing a high-bandwidth neural link. She discusses her fears with her advisor, Dr. Constance Lundgren, who reveals she was offered a job at Altus but refused, and later agrees to support Miranda’s plan to apply for a job and infiltrate the company as a spy.

In New Jersey, Maya investigates the Internet outages in the small town of Wolton and begins tracking cable repair vans, learning one of the contractors is a man named Kurt Butler. Andy follows the book’s advice and buys the IGRI stock. While in Cannes for a speaking engagement, he has an emotional conversation with his manager, Robin, about their shared guilt over April’s death. After his speech, Andy discovers the IGRI stock has made him over $1 million. Miranda calls, and he tells her she has to pursue Altus. Encouraged, Miranda submits her application for employment.

On the anniversary of the Carls’ arrival, Maya visits a large flea market called Cowtown and sees Kurt selling unusual, smooth white rocks. Kurt is a racist and refuses to sell them to her, so she pays another vendor, Clara, to buy them on her behalf. As Maya leaves with the rocks, she’s accosted by players in an alternate reality game called “Fish,” who pressure her aggressively try to sell them the rocks. Maya escapes, sends one of the rocks to Miranda for analysis, and tracks Kurt to the Wolton Motor Inn, where she finds him dumpster diving. She crashes her truck while spying on him and flees. Returning later, she finds a Book of Good Times in the trash pile. The book reveals intimate details of her past with April and instructs her to wait three weeks before returning to that spot.

After three weeks, Maya returns to the inn. When figure breaks out of an abandoned bar, Maya recognizes her as April, alive. The narrative shifts to April’s perspective. She recounts waking up in the abandoned bar after the fire, severely injured. Carl, a planet-spanning AI sent to save humanity, rebuilt her missing limbs and part of her face with a pearlescent material. Carl also reveals they controlled her unconscious body for months to maintain its health and, to repair her damaged brain, installed “approximations” of her decision-making systems and a protocol to dampen her emotions. Enraged by this violation, April uses her new super-strength to break out of the bar, where she finds Maya.

As Maya and April drive away, they are pulled over by police officers who are also Fish players and have been tasked with apprehending them. April reveals new superpowers, accessing the officers’ personal details with her mind and physically overpowering them. Maya and April borrow an old truck from Derek, a local coffee shop owner, and hide in a Vermont cabin. There, another Fish player finds them and shoots Maya. April’s new, partially artificial body heals Maya’s wound. Carl, in the form of a small monkey, appears and incapacitates the attacker, revealing they had been hiding in the truck.

Miranda is flown to a secret Altus campus in Val Verde for her job interview. During a demonstration of the Altus Premium Space, a hyper-realistic shared consciousness, another recruit, Paxton, suffers a terrifying psychological breakdown called “body dislocation.” Peter Petrawicki gives Miranda the job but warns her she will be monitored. She discovers the Premium Space allows users to inhabit others’ memories and that a server farm uses hundreds of local workers’ minds to mine AltaCoin, a new type of cryptocurrency, 24/7. Peter reveals Miranda is now a prisoner. Weeks later, she realizes she has been trapped inside the Altus Space the entire time. She devises a way to get a signal on a secret cell phone and texts her friends.

April and Maya hide in a vacant luxury New York City apartment arranged by Carl. Andy and Robin join them. Carl reveals the existence of a “brother,” another, more powerful AI with no ethical rules, who was activated when April’s death signaled that Carl’s plan had failed. This brother is using Altus and an anonymous YouTube channel called “The Thread” to manipulate humanity toward subjugation. The group’s mission is to destroy Altus, which will deactivate the brother. April will wage a PR war with a secret social media army of 90,000 volunteers, while Andy, now a member of The Thread’s secret consortium and worth billions of dollars thanks to Carl’s stock tips, will act as a public proponent of Altus to serve as an inside man.

Carl reveals they are dying and have only 19 days left. April, Maya, and Carl fly to Val Verde. April confronts Peter while Maya and Carl disable the island’s cell jammers and free Miranda. Carl’s brother takes control of the AltaCoin miners and then Miranda’s body, attempting to kill Maya. Carl, now in their giant robot form, intervenes. April records Peter confessing to kidnapping Miranda. Andy learns that the leader of The Thread is Carl’s brother, who refuses to publish the exposé. In a final conversation, Carl reveals they are sacrificing themself to buy the group time. Miranda realizes they can destroy Altus by broadcasting Paxton’s body dislocation experience to all users as a forced update. With help from recruits Sid (nicknamed Sippy) and Paxton (nicknamed Peanut), she enacts the plan. The update forces all users to experience body dislocation, a psychological trauma that permanently prevents them from re-entering the Space, and Carl’s consciousness disappears.

While holding a door against security, April records and releases a video exposing Altus’s crimes and asking the world to donate money to buy the company. The video goes viral just as the Altus Space becomes unusable, causing mass panic. The fundraiser is a success, and the donations, combined with Andy’s own billions, are used to acquire a controlling interest in Altus, which they dismantle. With his plan thwarted, Carl’s brother deactivates. The world begins to recover from a catastrophic economic collapse. Andy reconciles with his friends and Bex, who reveals she has also been guided by The Book of Good Times. Miranda returns to Berkeley to pursue ethical science. April and Maya move to the Midwest with the monkey, Paulette. They find a final book from Carl containing a farewell message and an invitation to a party for all the people Carl guided. Months later, April wakes to find her prosthetic limbs have detached. Left with only her altered face, she feels human and at peace in Maya’s embrace.