Based on the popular podcast of the same name, this novel is set in Night Vale, a small desert town where surreal and dangerous phenomena are treated as everyday occurrences. The story follows two women whose separate mysteries draw them together and toward a place called King City.
Jackie Fierro runs Night Vale's only pawnshop. She has been nineteen years old for as long as she can remember, possibly decades or centuries, since time does not work properly in Night Vale. Her life consists of the shop's rigid rituals and evenings spent listening to Cecil Palmer's community radio broadcasts. One evening, a man in a tan jacket carrying a deerskin suitcase pawns a slip of paper with the words "KING CITY" written in smudged pencil. After the transaction, Jackie cannot remember the man's name or face, and the paper is stuck permanently in her hand. She burns it, locks it away, and dissolves it, but it always returns. She resolves to find the man and force him to take it back.
Diane Crayton is a single mother raising her fifteen-year-old son, Josh, a shape-shifter who changes form constantly, sometimes appearing as animals, insects, furniture, or a short, chubby human boy with glasses. Despite his many forms, Diane always recognizes him. Their relationship is strained by Josh's growing curiosity about his absent father, Troy Walsh, who left Night Vale when Josh was a baby.
Diane's mystery begins at work when her co-worker Evan appears at her desk wearing a tan jacket, staring past her and extending a slip of paper toward her. Simultaneously, Evan calls on the phone to say he cannot come in. After this encounter, Evan's cubicle is replaced by a plant and an empty chair. No one at the office, including Diane's boss, Catharine, remembers Evan ever existing.
Jackie searches for answers. She visits Old Woman Josie, an elderly resident who lives with beings called Erikas (angels, though acknowledging their existence is illegal in Night Vale). Josie reveals that she and the Erikas also have papers they cannot put down and warns that the man in the tan jacket comes from a dangerous place. Josie directs Jackie to the library but cautions against following the man to his city. Jackie also consults Carlos, the local scientist and boyfriend of radio host Cecil, who confirms that no roads connect Night Vale to King City. Mayor Dana Cardinal is sympathetic but unable to help.
Meanwhile, Diane starts seeing Troy everywhere: at a gas station, a bank, a movie theater, driving a police car. Each Troy holds a different job and never acknowledges her. Josh, unbeknownst to Diane, has enlisted a friend to trace information about his father through city records. Evan later contacts Diane through mysterious texts and a meeting at the Moonlite All-Nite Diner she cannot fully remember. He gives her a "KING CITY" paper, tells her to pass it to Josh, and points out Troy working at the diner, connecting Troy to everything happening.
Jackie and Diane's paths collide when Jackie chases Troy through the diner and Diane shouts his name from the parking lot. They crash into each other, letting Troy escape, and part furiously. Jackie discovers that Troy exists as multiple identical copies throughout Night Vale, each holding a different job. She begins tracking them, but none will speak to her. Diane, placed on permanent unpaid leave after breaking into Catharine's office to search for Evan's records, continues pursuing Troy alone.
Despite their animosity, both women independently decide to visit the Night Vale Public Library, an extremely dangerous location guarded by monstrous librarians, massive creatures with toxic tendrils and multiple jaws. They arrive simultaneously and agree to enter together. Diane finds Troy's file, containing a photograph of him posed in a Night Vale that has not existed for over a hundred years, his arm around an unidentified little girl. Jackie retrieves a shoe box from the Forbidden Materials shelf with contradictory newspaper articles about King City. A librarian attacks Jackie, wrapping a poisonous limb around her neck, but Diane stabs the creature with a jagged rock and frees her. They crash through the library doors and escape.
Shortly after, Josh takes Diane's car and runs Jackie off the road, sending her to the hospital with a broken arm and the "KING CITY" paper sealed inside her cast. Josh disappears. Diane searches his room and finds papers covered in "KING CITY" in his handwriting, confirming he has gone to King City.
Jackie visits her mother, Lucinda, who reveals that Night Vale's broken time caused Jackie to spend decades or centuries frozen at nineteen, forgetting her mother and her childhood entirely. Lucinda also reveals that Troy is Jackie's father, making Josh her half-brother.
Diane's attempts to reach King City all fail: Buses, cars, and planes loop her back to Night Vale. She appeals to Jackie, and despite her injuries, Jackie agrees to help. They take a Mercedes from the pawnshop's inventory. After hearing on Cecil's radio show that plastic flamingos from a local store cause people to jump through time and space, they steal several from Carlos's lab. Touching the flamingos as they drive, they are transported to King City.
King City is deeply wrong. The streets are nearly empty, a roaring hum fills the sky, and Diane feels herself splitting into multiple simultaneous lives, becoming less present with each iteration. The stores contain decaying merchandise and citizens trapped in a crumbling reality. Jackie spots Troy and chases him while Diane enters City Hall alone.
Jackie follows Troy to a bar where every person inside is Troy, dozens of identical blond men, none of whom recognizes her. Diane meets the man in the tan jacket, who is the mayor of King City. He explains that Troy came from Night Vale, and his ability to multiply gradually overwhelmed the town. As the Troys proliferated, citizens became forgetful, unable to leave, and the town slipped out of sync with reality. The mayor traveled to Night Vale seeking help but was forgotten by everyone he encountered. He lured Josh to King City, believing that studying Troy's son, a boy of many forms but one self, could help reverse what Troy had done.
Jackie finds Josh in the building and brings him to the mayor's office, where Diane embraces her son. The mayor demands that one of Troy's children remain to help. Jackie volunteers, but Diane refuses, arguing that the problem is Troy's and Troy must take responsibility.
They go to the bar and call every Troy outside. Diane demands he return to Night Vale and leave King City. Jackie tells him his compulsive helpfulness is selfish. Josh, speaking to his father for the first time, says he would be open to knowing Troy, but Troy must live in Night Vale, all of him, and must earn the relationship. The Troys retreat into the bar. After a long pause, one comes back out and nods at Josh. The rest follow, one by one.
Months later, the Troys have settled in Night Vale. Carlos devises a solution: Each Troy is issued a flamingo that shifts him into a separate reality, preventing further destructive multiplication. Jackie hires Diane as a part-time bookkeeper at the pawnshop, giving Jackie free time outside the shop for the first time. Jackie begins visiting Lucinda regularly and celebrates her twenty-first birthday, having decided to age on her own terms. At a barbecue at Lucinda's house, Josh, in a winged form, flies above the rooftops at Jackie's encouragement. Troy watches from his car, having made a decision the narrative leaves unstated. Jackie calls up to Josh that he can go way higher than he thinks.