Josh's problem arises one night at a carnival. He sees a girl he likes waiting in line for one of the more dangerous rides and nervously approaches her, despite his prepubescent stature. She introduces him to Derek, her much older and more mature date. Josh is ultimately rejected by the taller girl and ride operator, and flees in embarrassment, bitter with his current station.
Josh wanders alone for a while, and stumbles upon a strange arcade-style fortune telling game called “Zoltar Speaks,” in which the player attempts to shoot a quarter into the mechanical fortune-teller's mouth in order to have his or her wish granted. Josh accomplishes this feat with little difficulty, as he is proficient with games, toys, and the like. His recent rejection still on his mind, Josh wishes to be "big;" in essence, Josh inadvertently wishes away his childhood. Zoltar gives Josh a card which reads, "your wish is granted" just as Josh discovers that the machine had been unplugged the entire time.
In an eerily Kafkaesque scene, Josh awakens the following morning completely transformed into a fully grown man, and like Gregor Samsa from "The Metamorphosis," makes a futile attempt to continue life as usual. In an effort to reverse the "spell" Josh puts on some of his father's clothes, ducks out of his house, and frantically rides his bike to the carnival site, only to find that it is completely deserted. With nowhere else to go, he returns home, and in his desperate condition, does what any 13-year-old does when faced with an "adult" problem; he tries to ask his mother for help. Needless to say, she does not recognize her son in his new form, and mistaking him for an intruder, expels Josh from his home.
Alienated by the world, Josh realizes that his only hope is to convince his best friend Billy of his identity, and so he sneaks into school to meet with him. At first, Billy's reaction is quite similar to Josh's mother's, but he starts to believe Josh when he recite the song the two boys sang at the opening of the film. The boys realize that Josh can no longer stay in their town because the police are looking for him, so Billy steals some money from his father to help Josh look for the "Zoltar Speaks" machiine in the Big Apple. They use the money to rent a small hotel room in a low-income area where Josh can stay while they look for the mystical Zoltar machine.
As the search for Zoltar continues on, Josh finds that he needs a source of income to pay for his room. He and Billy search the newspaper and find a low-level opening at the MacMillan Toy Company. The following day Josh meets with a MacMillan representative for a job interview with a with a desperately forged resume. The interview, which goes surprisingly well, is interrupted by a strong, authoratative, female executive named Susan Lawrence. At that moment, during an angry rant about her incompetent receptionist, Josh falls in love with her and begins his second metamorphosis.