Nilly is new to the neighbourhood, but 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 an extra-strength dose of fart powder that shoots them up into a tree! It's all good farty fun. That is, until someone steals the industrial-strength fart powder. Now Doctor Proctor's ticket to fame is in the hands of an enemy with evil intentions...