A mysterious arrival at Kirrin Cottage, in the middle of the night, sparks excitement amongst George and her cousins. Berta is a vulnerable, young American girl, (daughter of a rich man) who is fleeing kidnappers and the Kirrin Household have been personally asked to protect and disguise her. In order to make her unrecognisable, Berta is transformed into a handsome looking young boy called Lesley—and the Five are constantly on the look out for potential kidnappers. Will the disguise be successful, or will Berta be recognised and therefore find herself in grave danger?