Ohrno Elementary's 5th grade class heads to the local aquarium, where John and Dave are intent on reuniting the school's prize-winning rainbow fish with its friends. When the class returns after John's shenanigans get the school permanently barred, the boys find the school empty. What dastardly evil is afoot? More importantly, can John and Dave stop it without Rubberband Boy's spectacular powers?
Armed with only his guts and an arsenal of rubber bands – and with the assistance of his timid companion, Clip Kid – Rubberband Boy must find a way to stop his evil new teacher and save his classmates from a horrible fate. But even if the two makeshift heroes succeed, what dangers await from the two mysterious figures in the background?