This, the third story in the series, is once again set in the seaside town of Kirrin. Julian, Dick and Anne arrive three weeks into their summer holidays after having been away with their own parents.
Upon their arrival, they meet the new cook, Mrs Stick, a sour faced woman with an obnoxious son called Edgar. Their usual cook, Joanna, was looking after her mother who had broken her leg. The Sticks prove to be thoroughly awful and things go from bad to worse when Aunt Fanny is taken ill and has to go into hospital leaving the Sticks in charge. With the arrival of Mrs Stick's husband things become positively unbearable and the Five decide to "run away" to Kirrin Island and look after themselves until their Aunt and Uncle return.
Whilst at Kirrin Island, they are shocked to see the Sticks there and think they may have come looking for them. But the Five find a hidden cave on the far side of the island and make their home in it, hidden from view.
One night they hear a child's scream and discover a case
containing the clothes and belongings of a small girl. It then
becomes clear to them just as to why the Sticks were on the island - it was to carry out a kidnap!
Locked in the dark dungeons of Kirrin Castle they discover a young girl, Jennifer Mary Armstrong, the daughter of
millionaire Harry Armstrong, and rescue her, then set about turning the tables on the dreaded Sticks.