Rupert P. Brown III is a scientist. In his room he has an aquarium experiment, a turtle experiment, and a nutrition experiment (two guinea pigs). But when he starts fifth grade, things happen that he has to label “No known way to prove scientifically.” The new teacher, Miss Switch, has eyes in the back of her head. She can control spitballs and water fountains. Eventually, Rupert discovers her secret: Miss Switch is a witch.
As they begin fifth grade, Rupert and Amelia discover that their teacher, Miss Switch, is a witch. Using his scientific mind, Rupert helps her solve a spooky dilemma. In return, the witch teaches Rupert and Amelia some magic. But soon Miss Switch disappears, and another teacher takes her place. One night that winter, a dark figure delivers a strange bottle to the children. Scientific curiosity leads Rupert to take the cork out. Suddenly, the bottle releases an ugly demon, Mordo, who plans to kidnap a whole class from Pepperdine Elementary School.
Rupert P. Brown’s biggest worry about sixth grade is it might be, well, a little bit dull. After all, how can a fellow be expected to top a fifth grade year in which his best friend was kidnapped, and he found out his best teacher ever was a real, honest-to-goodness witch? But when Rupert types the word "computowitch" in an e-mail message, his screen goes all green, and then his parakeet starts giving him math lessons. He knows it can only mean one thing: Miss Switch is back!