The girls welcome Bill and her horse, Thunder, to Malory Towers, but Bill’s place in the third form is under threat when she is accused of spending too much time in the stables. Gwen’s father is offered the position of head of board at the school.

Darrell suggests a midnight feast in the stables, but they’re afraid of horse poachers. Mavis, a sixth former, is on the hunt for someone to accompany her on the piano for an important audition, and Irene might fit the bill.

Bill struggles to balance her schoolwork with time spent at the stables with her horse, Thunder. Bill and Darrell need Thunder's help when someone at the school has a serious accident.

Miss Johnson enforces a list of tough new rules which get the better Darrell’s temper. An important lacrosse match is at stake when Darrell is given a particularly difficult punishment.

Sally returns to a very different Malory Towers after her case of the mumps. The strict new rules keep Mavis and Irene from their audition, but the girls have a plan to cover for them and keep Miss Johnson at bay.

Gwen goes a little overboard when she organizes a dance lesson with the Thackerton boys. Mary-Lou discovers a mysterious statue in the woods when Gwen asks her to break the rules to gather ivy.

Darrell’s sister Felicity visits to take an exam that will determine her acceptance at Malory Towers. Darrell wants to enjoy time with her sister but Miss Johnson's strict rules stand in the way.

Alicia sends a package for the girls filled with goodies and prank materials, plus a secret message. Darrell prepares for the lacrosse trial and sneaks in practice time.

With the third form on a trip to the circus, Darrell and Sally attempt to recover the confiscated peaches from Miss Johnson’s office, but they find more than they expected...

Bill will stop at nothing when she discovers that her horse Thunder is sick with colic. Gwen is charged with keeping Bill away from the stables or else they will both be punished.

Ron shows Darrell and Sally a stash of art found in the stables, but where did it come from? Miss Johnson is caught off-guard when Miss Grayling arrives back at Malory Towers.

With Darrell focused on clearing Ron’s name, Mary-Lou and Ellen uncover new information that changes everything they thought about the art thefts.