Mildred is looking after 'Bonzo', who is Ruby's cyberpet (well, at least it isn't one of those ruddy Tamagotchis!). After the potion lab is destroyed, Bonzo goes missing.... Ethel's dad, who's on the board of directors, visits the academy, and convinces the teachers to set up a computer system. Bonzo makes his return, but he has been affected by magic as a result of the potion lab's destruction.... Bonzo connects up to the computer system and uses it to hypnotize everyone to try and help him take over the world when the system is connected to the net.... Mildred, with some help from a third year, are able to break Miss Hardbroom from the spell who then proceeds to defeat Bonzo just in time!