Wayward Son, the second installment of Rainbow Rowell's Simon Snow trilogy, picks up more than a year after the events of
Carry On, in which Simon Snow defeated the Insidious Humdrum, a magical threat that drained magic from the world, by sacrificing all of his own power. Simon is left with no magic and a pair of leathery red dragon wings and a tail, remnants of a self-transformation spell he cast during the final battle, which he cannot shed.
Simon now spends his days on the sofa in the London flat he shares with his best friend, Penelope Bunce, drinking cheap cider and refusing food, conversation, and affection. His boyfriend, Baz Pitch, a vampire who is also a gifted magician, watches Simon's decline with growing helplessness. Their physical intimacy has eroded: Months ago they kissed freely, but now Simon flinches from touch. In his own chapters, Simon reveals he plans to break up with Baz, believing Baz stays only out of pity.
Before Simon can act, Penny bursts in with a plan: She has bought plane tickets for the three of them to visit Agatha Wellbelove, Simon's ex-girlfriend, who moved to San Diego after the war and has stopped returning Penny's texts. Simon resists, citing his wings and his nonexistent passport, but Penny has invented a spell that temporarily makes his wings disappear and has forged his travel documents with magic. Baz reluctantly agrees to join, and Simon, tempted by an old dream of an American road trip, gives in.
In San Diego, Agatha has deliberately distanced herself from the World of Mages, the organized magical community in which she was raised, leaving her wand behind in England. She has befriended Ginger, a warm, New Age believer in auras and self-optimization. Ginger's wealthy boyfriend, Josh, belongs to NowNext, an exclusive self-improvement organization whose members hold retreats devoted to maximizing human potential. Ginger secures invitations for both of them to an exclusive NowNext retreat. Agatha finds the group's rhetoric about conquering mortality ridiculous but agrees to attend for Ginger's sake.
The trio flies into Chicago so Penny can see Micah Cordero, her long-distance boyfriend since he was an exchange student at Watford, the magickal boarding school they all attended. Micah tells her he has already broken up with her multiple times, but she never listened. Penny walks out, devastated.
They begin the drive west in a rented 1968 Mustang convertible. Baz teaches Simon to drive a manual transmission, and the patient lesson becomes the closest emotional connection they have shared in months. Baz also discovers that his British-idiom spells do not work in America because there are not enough Normals, or non-magical people, using those phrases locally.
At the NowNext retreat, held in a gated compound, Agatha meets Braden, one of the organization's founders, who is charming and intrigued by her cynicism. Meanwhile, the road trip begins to revive Simon's spirits. At a Renaissance Faire in Nebraska, his wings burst free when a bell breaks Penny's concealment spell, but the costumed crowd assumes they are part of a costume. He and Baz flirt openly and share a rare moment of lightness. Then Baz detects real vampires among the fairgoers. When the vampires attack, all three fight in full view of the crowd and flee while the audience applauds, believing the battle was staged. Simon, exhilarated, kisses Baz passionately against the car, their first real kiss in months.
That night, a silver pickup truck follows them across Nebraska. They enter a Quiet Zone, a magicless dead spot in the sparsely populated Great Plains, and the Mustang's magically fueled tank runs dry. The truck's driver emerges: Shepard, a young Black man who identifies himself as a Normal who knows about the magickal world. Before they can deal with him, a posse of American dark creatures, including a were-skunk with a shotgun, accuse them of trespassing. A brawl erupts. Shepard drives them all to safety, though Baz takes a chestful of buckshot.
In the Colorado mountains, a dragon named Margaret, who takes the form of an older woman, captures and binds all three after Baz kills one of her sheep to feed. Margaret identifies Simon's wings as those of a dragon hatchling and calls Baz a "Next Blood" hybrid, a term for a new kind of vampire she considers dangerous. The group convinces her they are harmless, and she releases them. Baz then negotiates an alliance with Shepard: He will serve as their guide in exchange for answers about magic, bound by a spell preventing him from sharing their secrets.
Back at the NowNext compound, Agatha's situation deteriorates. Braden moves her to the members-only wing without consent, confiscates her phone, and reveals he knows she can do magic. When she tries to leave, the door is locked. Braden bares fangs, revealing himself as a vampire, and sedates her.
Penny recovers a voicemail from Agatha whispering about Braden before men's voices discuss moving up "the extraction." The group presses west. At the Hoover Dam, Shepard introduces them to Blue, a river spirit who directs them toward Las Vegas and recognizes Simon as "the drain," the former vessel of the Humdrum who once consumed the world's magic. In Las Vegas, Baz infiltrates a vampire party at the Katherine Hotel and meets Lamb, a centuries-old vampire who serves as the elected leader of the city's vampire community. Lamb reveals that Las Vegas is effectively vampire-run, its vampires feeding on tourists without killing them, a revelation that stuns Baz, who has always believed feeding means killing. Lamb also teaches Baz to retract his fangs through willpower. At a second meeting, Lamb explains the Next Blood: They are wealthy Normals who demanded to be Turned into vampires and are now pursuing the transplantation of magical abilities by experimenting on captured magicians.
Lamb proposes an alliance against the Next Blood's facility near Reno. His convoy of 50 vampires drives the group into the desert, but Shepard, who was hypnotized into sleep by Lamb, wakes and warns them they are entering another Quiet Zone. It is a trap: Lamb has a treaty with the Next Blood requiring him to turn over any mages who enter Las Vegas.
At the bottom of a sand dune, Agatha stands with her hands bound, flanked by NowNext vampires armed with automatic weapons. They shoot Simon out of the sky. Penny and Agatha are captured with their mouths sealed shut. Baz, held by Lamb, is devastated. When a NowNext vampire bites Shepard, the vampire immediately dies: Shepard's soul belongs to a demon through a curse, making his blood lethal.
Agatha spots the distant procession of the Burning Lad Festival, a gathering of tens of thousands of Normals in the desert. Drawing on their ambient magical energy, she casts a fire spell without a wand or voice, burning the vampire guarding them. Penny retrieves her swallowed amethyst gem and casts a spell transforming all the guns into farm implements. Baz attacks Braden with his bare fangs, and Lamb, initially restraining Baz, switches sides when the Next Blood fire on them both. Simon drags himself up, and Penny and Agatha channel their combined magic to destroy the remaining Next Blood vampires. Lamb asks Baz to stay with him, arguing Baz will never belong among mages. Baz refuses.
Shepard drives them to San Diego. Penny heals Simon's injuries. Agatha, shaken, decides to return to England to retrieve her wand. Penny discovers that Shepard is cursed, his soul belonging to a demon, evidenced by black rune markings on his arms, and insists he come to London for help.
On the San Diego beach, Simon tells Baz he should stay in Las Vegas, where he would not have to hide his vampirism. Baz replies that he would not be happy anywhere without Simon. Simon privately resolves to stop pretending he is a superhero and considers having his wings and tail removed so he can live a Normal life. The thought feels "awful, but clean." Penny interrupts with urgent news: There is trouble at Watford, and they must return to England immediately.