In Greentown, Illinois, a small town enjoying the innocence of an upcoming autumn as the days grow shorter, two young boys—reserved Will Halloway and somewhat rebellious Jim Nightshade—leave from an after-school detention for "whispering in class" and hurry off for home. When the boys hear about a strange traveling carnival, Mr. Dark's Pandemonium Carnival, from a lightning-rod salesman, they decide to see what it is all about, but Will is fearful, as most carnivals end their tours after Labor Day. When the ominous Mr. Dark, the Illustrated Man, rides into town on a dark midnight, setting up his massive carnival in a matter of seconds, the boys are both thrilled and terrified. It seems to be just another carnival at first, but it is not long before the forces of darkness begin to manifest from the haunting melodies of the carousel—which can change your age depending on which way you ride it—and from the glaring Mirror Maze. With his collection of freaks and oddities, such as the Fat Man, Mr. Electro, and the blind Dust Witch, Dark intends to take control of the town and seize more innocent souls to damn. It will take all the wit and hope of the two boys to save their families and friends, with aid from an unlikely ally, Will's father, the town librarian, who understands more than anyone else that "something wicked this way comes".