Jack feels so humiliated by the fact that his father is the school janitor that he decides to get revenge by smearing a desk with gum. When he's caught, his punishment is to scrape gum off desks for three weeks after school, leading to discoveries about his dad's past.
By fifth grade, Jack has learned to be embarrassed by his father's profession--janitor. When Jack begins class in the building where his dad, John, is head custodian, Jack's worst nightmare comes true. The other kids find out, in an especially humiliating way, what his father does for a living. Blaming his father, he decides to get revenge. He determines what is the stickiest and smelliest gum (Bubblicious watermelon flavor), chews up thirteen pieces, and smears them all over the bottom of a desk and onto the seat, knowing full well who will have to clean it up.
But he is caught, and his punishment is to spend three weeks after school helping out his father by scraping gum off desks, starting with the one he so efficiently ruined. This begins a voyage of discovery for Jack into the hidden recesses of the school and of his father's past.