Nilly is new to the neighborhood, but he is quick to make friends: Doctor Proctor, an eccentric professor; and Lisa, who is teased by the twin terrors Truls and Trym. Nilly and Lisa help Doctor Proctor develop his latest invention, a powder that makes you fart! The powder makes Nilly and Lisa very popular at school when they sell it for fifty cents a bag. And they get revenge on Truls and Trym by giving them a dose of extra-strength powder that shoots them up into a tree. All is good fun… until someone steals the industrial-strength powder—which was supposed to make Doctor Proctor famous—to use for evil purposes…