"The grown-ups aren't telling us the whole story, so we've got to find it..." When best friends Siddy and Zadie start the year at the magical School for Fireflies, they discover they are anything but normal. Amidst the excitement of new powers and potions, there is a decades-old mystery waiting to be solved. The girls must put their detective skills to use to secretly find a long-lost diary. And they soon realise that the clues they uncover might be tied to the reason Siddy's dad disappeared without a trace...