Julian, Dick and Anne arrive in Kirrin Cottage to stay with George (real name Georgina) for the holidays.

They plan to spend time exploring Kirrin Island but their happiness is spoilt when Aunt Fanny falls ill and has to leave with Uncle Quentin to be treated in a far-off hospital.

After tormenting the Sticks into a retreat, the children rescue the girl and take her to the police, who are amazed to see the child that "the whole country is looking for."

Jennifer Armstrong and her family are never mentioned, although the Sticks kidnap George and Dick before Julian and Anne rescue them.

Jennifer's kidnapping is shown as she is snatched from her bed, then bound and gagged and left in the cave before the Five rescue her.