On Dara’s birthday, an invitation comes from their cousin Violet; come stay on Bardsey Island for a week, stay at their cottage, and celebrate Halloween. And bring all your friends! Vivi can’t refuse an opportunity to go back to Wales, and her friends are immediately excited for star-spotting, foraging, hiking, and just general adventuring. Little do they know, they are about to be thrown into a huge high-stakes treasure hunt, with the fate of the world resting on them (again). And Vivi’s feeling that Arawn is just waiting to reappear is only growing stronger.