When Julian, Dick and Anne arrive at Kirrin for the latter half of their holidays they find the cook from Kirrin Cottage, Joanna, has gone to look after her mother, who broke her leg, and in her place is Mrs. Stick, complete with her rude son and horrible dog, Tinker (who is nicknamed Stinker by George).
When George’s mother takes ill, and her daddy goes to stay at the hospital with her, the Five are left alone with the Sticks. When Mr. Stick arrives at Kirrin everything starts to get awful. The Sticks get so annoying that they decide to run away to Kirrin Island.
At Kirrin Island, they find the roof of the one liveable room in Kirrin Castle has collapsed, but they find a cave to live in instead.
One day, though, they find the Sticks on the island! Soon it is clear that they are not looking for the children, though. Then what are the Sticks doing on the island? When the Five see lights out to sea, at night on the island, they are sure they’re mixed up in smuggling.