Darrell and her class return to Malory Towers. The first order of business: elect a new class leader. Gwen decides to take the new girl under her wing and become her best friend.

Alicia convinces Darrell to help her play a prank on their teachers with invisible chalk. Meanwhile, Mr. Parker becomes stricter with his teaching. Mary-Lou finds her voice and stands up for herself.

The girls attempt to make Ellen feel more included but their efforts backfire. Miss Grayling has a secret that might put Malory Towers in danger.

In an attempt to impress her parents, Gwen auditions for the lead role in the upcoming school play. Darrell and Sally devise a plan to save the school.

When Alicia’s birthday gift from her parents doesn’t arrive, she takes it out on her teachers. Gwen becomes more tangled in her lies.

Ellen is stressed that she’ll lose her scholarship and stays up all night studying for an exam. Gwen gets her hands on Darrell’s diary and discovers Darrell's secret.

Darrell shows a potential investor around Malory Towers. Gwen is confronted with her lies when her mother visits.

A teacher and Gwen are quarantined after finding out they have the measles. Darrell finds out disturbing news about the future of Malory Towers. Sally takes on extra responsibilities.

Alicia and Darrell pull a sneezing prank on their French teacher, which disappoints Sally. Someone has stolen important possessions from the girls.

Malory Towers competes with the local boys' school in a competition. Ellen suffers a panic attack when she is accused of Gwen's misdeeds.

The girls doubt Ellen’s innocence. Gwen attempts to get rid of the items she stole, endangering Mary-Lou in the process.

Miss Grayling reveals disheartening news. In one last attempt to save the school, Darrell and Sally try to find Lady Jane’s lost treasure. Gwen’s secrets come to light.