Miss Hardbroom announces it is time for the school's annual pet inspection and Miss Swoop confides in Miss Widget that she has a crush on the Inspector, Mr Chalmers, although he never seems to notice her. But, Belladonna sees his visit as the perfect opportunity to finally get rid of Hettie's annoying dog, Kittie. She prepares a potion, which Kittie greedily devours and he starts to grow at an alarming rate. Very soon he is 40 foot high and still growing! Hettie needs to think (and talk) fast to keep her giant pet hidden from Hardbroom and the Inspector. As usual, Hettie is determined to be the best witch that the academy has ever seen, with a little help from her friends, Mona Hallow and Cressie Winterchild of course. There's two witches standing in their way however, arch rival enemy Belladonna Bindweed and teaching tyrant Miss Hardbroom.