Cathy Barnes was to be adopted by the Hansons and she was happy, but she discovered their daughter, Sara, had died from pneumonia after a cross country run. Mrs Hanson was determined to fuss and make sure nothing happened to Cathy. This was a problem for Cathy as she loved to be active and had joined the gym club at her new school.
Sally Lenton had just moved to the village of Hollybrook. Whilst exploring, she went to the grounds of Denby house and spotted an unhappy girl at the window. She found out the girl was Fran Halliday and her mother kept her a prisoner because she was afraid Fran may catch a dreadful disease and die like her elder sister did. Mrs Halliday agreed Sally could be friends with Fran on the condition she could not ever leave Denby house, as she didn’t want her to bring any germs in. With the help of Mrs Gill the housekeeper, Sally sneaks back to her mother and with her agreement, she goes back to Fran to stay for the school holidays.