After being selected as head of lower school, Darrell soon feels the demands of leadership when Felicity, her younger sister just starting at Malory Towers, gets into trouble.

Darrell enlists the help of the First Form students when facing her first challenge to her authority as head of lower school.

Preparing for the inter-tower lacrosse match leads to disappointment for Darrell and Felicity. The rest of the team speculates why breakout star Clarissa is hesitant to play.

Ruth lets her sister Connie take credit for her essay. The First Formers try to evade Darrell while searching for treasure.

The First Formers try to prank their teachers with Irene's help. Mademoiselle's reaction to the prank raises suspicions for Irene.

Alicia plans an outdoor midnight feast for her and Darrell. Felicity and June sneak out to search for a hidden room within Malory Towers.

Darrell struggles to prepare a speech she is to give in front of the whole school. Sally and Bill organize a lacrosse match. Irene’s father delivers news Irene has not been looking forward to.

June makes some itching powder for a prank that gets out of hand. Connie blames June for the unfortunate things that keep happening to her, even though June insists she had nothing to do with them.

When Clarissa receives troubling news that her pony has been sold, she breaks the rules to rescue him. Irene and Mademoiselle Rougier make efforts to strengthen their relationship.

Felicity and June prove to be a handful when Darrell supervises the class field trip. Meanwhile, Gwen gets more than she bargained for when left with Mr Parker's pregnant wife.

Darrell and her classmates await their exams while Felicity and June continue to explore the secret room. Gwen pretends to have heart issues to get out of the exam but then finds herself in a dangerous situation.

Ruth’s bullying of Connie reaches a new low when June is wrongly accused of playing pranks. Darrell encourages the lower form to find who is responsible and the whole class gets a lesson on accountability.

June and Darrell find themselves in danger when they leave the school to continue the search for the treasure in a cave during high tide. The rest of the school prepares for the wedding. Irene is given an important task by her father.