Horrified by Lorna's end of term report which says that the family baby is bumptious and self-satisfied, her mother Bess Carey decides she must leave small Bury House and go to Wynyards, the big day school where her cousin Kit Arnold is a prefect. This means that 13-year-old Lorna must also live with Kit and her aunt, Kath Arnold, during term time.
The contrast between her the large, careworn Carey family and the close-knit Arnolds, who are more like friends than mother and daughter, couldn't be more marked. Lorna is inclined to rebel at first at the expectation that she will help around the house, and her jaw drops more than once at her Auntie Kath's youth and informality. But this is nothing compared to the shock she gets at school. Used to making it to the top of the class in every subject with room to spare, Lorna finds herself having to work hard for every single mark if she is to keep up in the Upper Third at Wynyards.
Her self-assurance leads to a bitter quarrel with one of her form-mates and a punishment for fighting which will make it very difficult to keep her position in the form. What is more, Auntie Kath will have to tell Lorna's mother that Lorna has been in trouble at school, and Bess is quite likely to inflict her own punishment as well.
Lorna also falls foul of Ardath Penney, the second prefect who steps up to take head girl Mary Anson's place when Mary is injured in a fall. But this time Lorna isn't acting for herself, but to stand up for someone who has become very dear to her.
Lorna finally sheds the last of her babyish ways when death comes to her family and she must go home. The Lorna who returns to the Arnolds is beginning to grow up and will make her home with them from now on.
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