The young witch in training, Mildred Hubble, has a less than desirable start of her first year at Miss Cackle's Academy as she makes quick enemies with the prissy Ethel Hallow & the tyrannical Miss Hardbroom for arriving late on her first day! To make matters worse, Mildred quickly finds herself in deep trouble & is on the verge of being expelled!

The girls are told the legend of Sir Walter who died in a rainstorm centuries ago outside the castle. Whenever there is a storm Sir Walter is said to walk the corridors, looking for revenge! Now Mildred & the girls are out to see if the legend is true! Meanwhile the girls decide the quality of the food they're being served is poor & demand a change!

It's time for the presentation of the kittens which will sit decoratively on the end of each girl's broomstick when they fly! When Mildred's Tabby can't even cling on to her broomstick, Ethel lays into Mildred about how hopeless she is, Mildred has been pushed too far, & turns Ethel into a piglet! She escapes, & the race is on to catch it & turn her back, before Miss Hardbroom finds out!

When Mildred's attempts to revise her potion test notes fail, Mildred & Maud produce an invisibility potion by mistake, getting the duo into trouble! Mildred is determined lie low in an effort to stay out of trouble, but the Hallowe'en festival looms, & Mildred's class has been chosen to put on a flying display! A very cross Ethel decides to sabotage Mildred's broom!

Stopping to rest in the valley below Mildred comes upon a group of witches & hears them planning to take over Cackle's Academy! Mildred, thinking on her feet, turns all the evil witches into snails. Back at school, while Miss Hardbroom does not believe Mildred, Miss Cackle recognizes the description of the Chief Conspirator as her wicked & jealous twin sister, AGATHA.

Thinking that some extra responsibility might do Mildred good, Miss Cackle asks her to look after the new first year, Enid Nightshade. Soon Maud feels Mildred hasn't got time for her any more & goes off in a huff. To make matters worse, Enid sneaked her pet monkey into the school & he's on the loose! Now Miss Hardbroom thinks the roving monkey is Ethel & that Mildred is obviously responsible!

Miss Cackle's birthday is a day of legendary boredom! Enid, determined not to sit through the boredom, drags a reluctant Mildred into a store cupboard. Ethel notices & locks the door on them! Inside the locked cupboard Mildred is in despair - this is the last straw, she's bound to be expelled! With the help of a badly damaged broom, they may be able to escape!

A trip organized by Miss Drill is to be a strictly "no magic" camping trip. Things get even worse when the group encounters a Scout troop of mortal boys (Including Jay Baruchel) also camping in the woods. The two groups merge to compete together in team building activities. Soon though the "no magic" rule goes out the window, as Ethel is determined to win.

A summer heatwave has hit Cackle's & the girls are succumbing to the heat. Miss Cackle produces a magical soda, that is so refreshing it's all the girls can think about. Soon wanting more, Miss Cackle decides to have a contest to see who can make the best non magical soda. However Ethel decides performing a little bit of magic is worth beating Mildred.

After Mildred causes an accident in potions, the school requests funding for newer equipment. The School's administrator, who happens to be Ethel's father, thinks this is the perfect time to bring Cackle's into the modern age! After residual effects from Mildred's mistake mixes with the new technology causes an even bigger problem! Now they see modern technology is not all it's cracked up to be.

Mildred & her friends plan on sneaking out of boundaries & go to a nearby sweets shop! Meanwhile a greedy businessman & his kind hearted, but weak willed assistant plan on converting the surrounding woods, the shop & even Cackle's into a pollution spewing factory! Now with a little help from an also rule breaking Miss Cackle, the girls form a plan to save the day!

Chief Wizard, Egbert Hellibore & his three apprentice Wizards pay a visit to Cackle's Academy. The girls soon see how mischievous & underhanded the boys are & a prank war begins, with Mildred being blamed for it! Soon there will be a debate between the boys and the girls & Mildred finds the boys are using magical trickery to cheat! Now she plans on turning the tables on them!

It is nearly the end of Mildred's first year at Cackle's Academy & everyone is happy, except for Miss Cackle! She's short with all the students, particularly Mildred whom she threatens to expel. The girls soon learn that, it is in reality Agatha, Miss Cackle's evil twin, returned to take over the school! Now they must prove it to the other teachers & save the day!