George and her new friend Timmy the Dog are joined for the holidays by her cousins Julian, Dick and Anne. The Five set out to investigate a long-ago curse involving Kirrin Island, but it soon transpires they are not alone in their quest.
The theft of a priceless new code machine by enemy agents sends the Five on an eventful train journey up to Scotland.
The Five reunite at a hotel on Cragstone Ridge, where old foe Thomas Wentworth seeks their help. He has foreseen the murder of visiting jazz singer Cab Vee, and it is up to the Five to uncover just who is plotting to kill him.
