Mildred is fearing that Wednesday because Miss Hardbroom is visiting CBBC, so she enlists the help of Luella to make a potion that Miss Hardbroom would approve of. The vital ingredient for the potion, as Luella accidentally finds out, is 100 grams of sugar, and other additions to the potion include frog's legs, rat's tails and jellybeans - the jellybeans mean that potion has changed colour.
When Miss Hardbroom visits, everyone fears the strict look on her face, until she comes to Mildred's 'Worst Witch' room. Mildred allows Miss Hardbroom to taste the potion, and despite Luella's protests, Miss Hardbroom tastes it anyway and starts feeling a tingling sensation overcome her. She then screams and races around CBBC like a loonatic - she's gone crazy! She models the Gumbles like balloon animals, messes around with the controls in the control panel and plays the skeleton bones like a xylophone in the Operation Ouch room. She's gone completely out of control, and Mildred fears it was her fault, but actually it's Luella's as she poured too much sugar into the mixture by knocking over the sugar pot Mildred had on her desk. Mildred feels Luella's pride has been torn by this, and she forgives her friend. They start to devise a plan on how to get Miss Hardbroom to snap the hell out of it.
Miss Hardbroom approaches the storeroom however, and opens the door only to find a pile of crates fall on top of her. Mildred and Luella are shocked, and Mildred yells "Call 999!!"
Later, Miss Hardbroom ends up in hospital with a bandage round her head, but there are no injuries - the teacher on the other hand feels alright again, and back to her strict self. Mildred fears she'll punish her for a bad potion, but Miss Hardbroom approves the potion, as it reduced her fatigue and thanks Mildred for calling the hospital to save her, asking if she could make some more. Mildred agrees, but only if Luella doesn't add sugar this time. Luella blushes and says, "Don't blame me, I know a lot about spells because of her."
