It is one week before Halloween when thirteen-year-old Will Halloway and Jim Nightshade are approached by a traveling lightning-rod salesman named Tom Fury who predicts an epic storm. Mr. Fury has sold over one hundred thousand lightning rods to “God-fearing” customers, and he gives Jim one free of charge and instructs the boy to nail it high on his roof, or else he’ll be “dead come dawn.” Mr. Fury is quickly on his way, but Will and Jim are left anticipating a natural disaster, and they immediately nail the metal contraption to Jim’s roof. The boys then make their weekly run to Green Town’s local library, where Will’s father, Charles, works as the janitor. At fifty-four, Charles is old enough to be Will’s grandfather, and each time Will runs into him at the library it is a “surprise—that old man, his work, his name.” After checking out their books, Will and Jim run home through the center of town, and they are confronted by the faint sounds of carnival music and the smell of cotton candy. Then, an advertisement for a traveling carnival, Cooger and Dark’s Pandemonium Shadow Show, blows through the air and wraps around Jim’s leg, and it is supposed to arrive the next day. Will doesn’t believe it—carnivals don’t typically come to town after Labor Day—but Jim is hardly able to contain his excitement.
Later that night, Will overhears his parents talking about the carnival, yet he still doubts that one will be coming so late in the year. As the clock on City Hall strikes 3:00 a.m., Will wakes to the sound of a train engine pulling into town and the unmistakable music of a calliope. Will and Jim jump out of bed and race down to the railroad bridge just in time to the witness the carnival train pulling a “wailing” calliope with nobody sitting at the keyboard. As the carnival train stops in an open field, a mysterious hot air balloon materializes and hovers over the train, and a man dressed in black steps out of the train’s caboose. On his command, the “train comes to life,” and as clouds obscure the light of the moon, the circus poles and canvases are erected, inexplicably, almost instantly. By the time the cloud cover passes, the balloon is nowhere to be found. Will and Jim race back home to their beds, and they are convinced that Cooger and Dark’s is no ordinary carnival.
The next morning, Will and Jim wake early and run down to the carnival grounds, but despite their chilling experience the night before, Cooger and Dark’s appears to be “just a plain old carnival.” They boys run into Miss Foley, their seventh-grade teacher, and she is looking for her nephew, who is visiting from Wisconsin. Miss Foley goes into the Mirror Maze to search for him, and she is scared half to death when she sees the reflection of a young girl who looks eerily like herself as a child. The maze attendant guarantees Miss Foley that she was the only customer in the maze, and she goes home to rest. Will and Jim spend the entire day at the carnival, and they visit all the rides and attractions, except for the carousel, which has a sign claiming to be “out of order.” Unable to stay away, the boys snoop around the carousel anyway, and they are confronted by Mr. Cooger, the proprietor of the carnival. Mr. Cooger aggressively snatches Will and Jim of off the broken carousel by the scruff of their necks, but his partner, Mr. Dark, is kind and insists that Cooger put them down. He gives Jim a white business card that magically changes color from green to red, and he promises Jim that it will get him a free ride on the carousel once it is fixed. The boys then pretend to go home, but linger in a tree nearby, and they see Mr. Dark start the carousel—only it is running in reverse. Mr. Cooger then steps on the merry-go-round, and after twenty-eight turns backward, he steps off a twelve-year-old boy. Jim and Will follow Mr. Cooger as he leaves the carnival and goes to Miss Foley’s house, where he is posing as her young nephew, Robert.
Later, Will and Jim follow “Robert” back to the carnival, and when he gets onto the carousel to transform back into Mr. Cooger, Will accidentally knocks the control box. The ride is sent fast, and uncontrollably, forward, and Robert goes around well over one hundred turns. By the time the carousel stops, he is transformed into a decrepit old man. Will immediately calls the police and an ambulance, fearing that they have accidentally killed Mr. Cooger, but when help arrives, Mr. Cooger is posing as Mr. Electrico, one of the human oddities of Mr. Dark’s freakshow. Mr. Dark apologizes for the misunderstanding, and again gives Will and Jim free tickets to ride the carousel, but this time Will and Jim are rightfully convinced of the carnival’s evil—although that doesn’t mean that they don’t still want to ride the carousel and instantly become men.
That night, Will wakes with the sudden realization that Jim has taken the lightning rod off his roof, and suddenly the Dust Witch, Mr. Dark’s most powerful and dangerous freak, floats over the boys’ houses in the carnival’s hot air balloon and marks Jim’s roof with a streak of “evil mercury paint.” Will outsmarts the Witch by rinsing off her mark with a garden hose and then pops the balloon with his arrow, but it is clear that the carnival is actively searching for them, and the boys won’t be able to hide much longer. Will and Jim are no match for the evil of Mr. Dark and his freaks, and they must soon enlist Charles’s help. Charles turns to the books in the library to help defeat the carnival, but when Mr. Dark sends the Dust Witch to stop Charles’s heart and kill him, it seems Charles has no choice but to succumb to death. As the Witch corners Charles, he is struck by the sudden and uncontrollable desire to laugh, and as he collapses into hysterics, the Witch’s evil powers become useless. As Charles is busy fighting the Witch, Mr. Dark closes in on Will and Jim, and takes them back to the carnival to cash in on their free carousel ride.
Luckily, Charles is able rescue Will, and when Charles volunteers for Mr. Dark’s “World Famous Bullet Trick,” he insists on Will’s help. Instead of his initials, however, Charles carves a “crescent moon” into the bullet, symbolic of his own smile, and when he fires it at the Witch’s mouth, the happiness that it implies knocks her to the ground, instantly killing her. As Mr. Dark runs off, Will and Charles set off in search of Jim, but they must first pass through the Mirror Maze. Inside the maze, Charles’s reflection is impossibly old, and he doubts his ability to save Jim. However, as Charles sees the reflection of his son behind him, he accepts his age and the death that it implies and destroys the maze with a deafening scream that shatters all the mirrors.
Once outside the maze, Jim is already getting on the carousel, his eyes blank. By the time Charles stops the carousel and Will is able to pull him off, it appears that Jim is already dead. In the meantime, Mr. Dark has transformed himself into a nine-year-old boy named Jed and attempts to lure Charles to his death, but Charles immediately recognizes his disguise. Charles holds the boy close, “almost lovingly,” and poisons Mr. Dark with his goodness and love. Then, in an act of pure silliness, Jim and Charles revive Jim by dancing and singing, knowing it’s the only balm against the horror and fear that the circus breeds. After Jim is revived, Will, Jim, and Charles, run off together happily, away from the carnival grounds.
