The kids are engaged in a smelling contest. Whoever can make the best smell wins. The class brings a strange assortment of smells to use, from flower fragrances to a smelly pair of socks. They mix all of the scents, but when they are out of the classroom, Janet (Arnold's cousin) tampers with the sample by contaminating it with skunk scent. The class uses the bus to attack all of the skunk scent molecules during the contest in order to keep Flora Whiff (the contest director) from getting a smell that she doesn't want. By carefully eliminating each molecules as they come out of the scent conglomeration, the class assures their victory in the scent contest, to Janet's dismay.