George meets her match in this thirteenth Famous Five adventure: with Henrietta (or Henry, as she prefers to be called), who is intent on acting like a boy, and the first few chapters of this fantastic book are based purely on their disliking of each other. It seems as if George's cousins: Julian, Dick and Anne are in for an awkward time, when George refuses to let Henry join their company – but will the fiery tomboy prove to be more decent than George expected, when a mystery evolving around the atmospheric: Mystery Moor, emerges, and the children find themselves: yet again, caught up in another adventure!