The beginning of the Summer term brings the surprising announcement from the prefects that they have decided to choose the cricket team and tennis pairs from the lower forms to allow them to study for their exams. At first the girls are against this idea but they are talked round. Carnation proves to be excellent at tennis and when her form are asked to choose pairs for tennis trials she is selected along with Madge.
Birdie is also selected but is worried she won't succeed at the trials. This leads her to start a petition to have the pairs selected from the sixth form as before. She is called before the prefects who suspect she has an ulterior motive. As a result of this Birdie refuses to practise before the trials and performs badly. She is therefore not selected.
Carnation and the other Guides are taken for a tracking practise in the country. Strictly against the rules Birdie has arranged that she and her friend Joan visit a nearby lake with her brother. Although Birdie is not present, Joan feels she has to go and falls in the lake and she is rescued by Carnation. Birdie blames Joan for the trouble she is in and attacks her. A prefect witnesses this and it is decided that she is to be summoned to a Guide Court of Honour.
The day of Carnation's tennis match arrives but she is tricked into going to the Art Room by Birdie who locks her in. Fortunately she is released in time to take part in her match, as all three reserves are unable to play for one reason or another. Carnation plays well and gets her tennis colours but the afternoon is spoilt by Birdie's behaviour.
Following the Guide Court of Honour there is happier news when Carnation is awarded a silver medal for saving Joan's life at the risk of her own.
Carnation and Madge become like sisters and Carnation is delighted to become officially related to the Harleys when her aunt marries Madge's elder brother.