Miss Hardbroom announces it is time for the school's annual pet inspection; The animal inspector comes to inspect the girls' cats, Miss Swoop's owl and Hettie's dog. 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 to make him bigger than the castle, 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.