This adventure begins quite innocently as the Five start their summer holiday at Kirrin Cottage.
Uncle Quentin and Aunt Fanny leave the children in the care of Joanne, the cook, whilst they head off for a tour of Spain. Media interest in Uncle Quentin's latest discovery had
become to much for them to bare.
The Five meet a "ragamuffin" girl called Jo. Their first
meeting resulted in an angry exchange between her and George, but Jo takes a liking to Dick.
One night George disappears mysteriously. Everyone is
astounded when they find a ransom note demanding Uncle Quentin's latest notebook for the safe return of George. The Five link George's disappearance to Jo (and her unpleasant father).
Through a series of clues, they discover where George may be being held captive and set out to attempt a rescue. The trail leads them to a hidden cliff-top mansion where they
finally discover George. Things go very wrong, and the Five find themselves trapped in a cliff-side cave
Jo saves the day and turns out a be a true friend when she risks her own safety to help rescue George.