For months, Junior Brown, an obese adolescent, has been meeting secretly with his friend Buddy, a street-wise homeless boy who lives in an abandoned building, and a former teacher, now janitor, Mr. Pool. In the basement of the school building, Mr. Pool has rigged up a model of the solar system that rotates, illuminated in the dark. He and the boys discuss astronomy, math, and a vision of worlds to come while the boys skip classes and take refuge in their basement hideaway.

Junior is mentally disturbed; both Buddy and Mr. Pool know this and take care of him as they can. Junior's fiercely controlling mother exacerbates his obesity by serving him excessive helpings of food and feeding his fantasy that his father will return. She herself has asthma, which ties Junior to her as intermittent caretaker.

Junior has a musical gift, but his mother has removed the strings from the piano, so he practices on keys that produce no sound. Fridays he finds his way to the home of a demented old piano teacher who won't allow him to play her piano because of her delusion that a dangerous relative is hiding in her apartment. Ultimately the boys and Mr. Pool are caught in their marginal existence below the school.

They retreat to Buddy's urban hideaway where he cares for two other boys, teaching them how to survive. Buddy is convinced he can help Junior survive as well, with Mr. Pool's help. He knows that if he allows Junior to be retrieved by his mother or school officials, he'll be locked up in an institution where no one will recognize his gifts or his worth.