Jim Nightshade and Will Halloway, both nearly 14, are the young friends at the heart of the story. Born a minute before midnight on the day before Halloween, Will, whose name suggests the phrase "holy way," is less susceptible to temptation than his friend. Will lives with his mother and his father, Charles Halloway. His relationships are vital to the emotional content and plot of the novel. His relationship with his dad is marred by Charles's sense of being too old to be a good father. This is the driving force of Charles's sadness and dissatisfaction. Will's friendship with Jim is what saves Jim from the carnival. His love for his mother is the leverage Mr. Dark uses against him at the climax of the novel, causing Will to sob loudly enough to be found.
Jim Nightshade and Will Halloway, both nearly 14, are the young friends at the heart of the story. Born a minute after midnight on Halloween, just two minutes after Will, Jim lives up to his name; deadly nightshade is a poisonous plant. He is the darker of the two friends and more susceptible to temptation. Jim lives with his mother, who is a single parent with a difficult past. He feels the pressure of being his mother's only comfort and longs to get old enough to move away from home. He is intrigued by the sexual dimension of the adult world. His longing to enter the adult world and his natural recklessness make the carousel's ability to change a person's age a constant temptation. However, his friendship with Will is a force that acts in the opposite direction, pulling him away from temptation.
Charles William Halloway feels his 54 years heavily. After an unsettled youth and young adulthood, he married late and had a son. Older than other fathers in town, Halloway feels a great distance between himself and Will and worries he cannot do what other dads do—run, play catch, and the like. When the carnival comes to town, Halloway's dissatisfaction with his advanced age makes him susceptible to its temptations. Over the course of the novel, however, Halloway discovers both the advantage of age—experience and wisdom—and an acceptance of self and mortality that allow him to overcome temptation. His greater understanding of what it means to be good, and what wickedness is, helps Will and Jim escape Mr. Dark and his carnival freaks.
The villain of the novel, Mr. Dark is one of the proprietors of the carnival that comes to Green Town. He tempts susceptible townsfolk according to their darkest desires, and when they give in to this temptation they are transformed into his carnival freaks. Those he lures are anchored to his will when he tattoos their likenesses on his body. This is how he becomes the Illustrated Man. Of the two boys, Will Halloway and Jim Nightshade, Mr. Dark first targets Jim, whose life experiences, impulsive nature, and longing for adulthood make him vulnerable to the carnival's temptations—especially its carousel. But Jim's friendship with Will is an obstacle for Mr. Dark's plan. As the two boys learn more about the carnival's secrets, they become a nuisance, then a threat, to the carnival. Will, Jim, and Charles Halloway ultimately learn Mr. Dark's weakness: he feeds on fear and agony. In the final scene of the novel, Mr. Halloway leverages this weakness and kills Mr. Dark.