Darrell Rivers returns to Malory Towers for her School Certificate term, this time with her twelve-year-old sister Felicity. However she resents another new first-former who takes Felicity under her wing, Alicia's sly cousin June. Felicity seems to like June though, but has another sensible friend in her form. The next day Darrell is made head of the Upper Fourth, of which she is very proud to be. Two twin sisters arrive that day, Connie and Ruth Batten. Ruth is extremely quiet and shy, and worse Connie speaks for her and does everything for her.
A couple of days later, another new girl to the Upper Fourth arrives, the 'Honourable' Clarissa Carter. Because of this title, Gwendoline is determined to be her friend, but is soon telling her unkind tales about Darrell, Sally and the rest of her form. She is also envious of Clarissa's weak heart, which excuses her from all games except horse-riding.
Whilst the form are working hard for their upcoming exams, their form mistress Miss Williams lets them have a day off to go for a picnic. During this day, Gwendoline and Clarissa go to visit Clarissa'a old nurse, who has prepared an enormous tea for them. They take the food back to the other girls, who decide to have a midnight bathe and feast. Unfortunately for Darrell, June sees them and tips off one of the teachers about the feast. Because of this, Darrell is forced to resign as head of the form. Meanwhile, the lazy Gwendoline is worried that she might fail her School Certificate and decides to escape from school by pretending that she has a weak heart like Clarissa, and her mother takes her home at half-term. However her father discovers her cruel deception after a few days, and sends her back to school to do the exam even though she had never revised for it. Felicity also finds out just how cunning June can be and ends their friendship.
After the exams finish, Connie's things go missing or become mysteriously damaged, and the rest of the Upper Fourth are baffled as to who might have been playing these spiteful tricks. The final straw comes when Connie's beautiful riding crop is found broken and gashed, and Darrell begins to think deeply as to who might have done this. Suddenly she guesses who the culprit is, but as she is no longer head of the form, can she still solve the problem?
This synopsis report prepared by Liza Rosette