When shy Sam confesses to his protective older brother Rocky that he is getting pummeled daily by the towering school bully George, the two boys plan the perfect payback. They invite George on a birthday river trip tailor-made to end in the bully's humiliation. Rocky's pals Clyde and Marty and Sam's budding girlfriend Millie also join the journey, which starts almost immediately with misgivings. Seeing George in a new light, as a lonely kid desperate for friendship and attention, Sam wants to call the whole thing off. But the boat and the plot are already in motion, and no one can foresee the surprises and accidents that are to come.