Emily Vole makes headline news in the first weeks of her life, when she is found in an abandoned hatbox in Stansted Airport. Then, only a few years later, her neighbour Mrs String dies leaving Emily a mysterious inheritance: an old shop, a small bunch of golden keys and a cat called Fidget. It's the beginning of an adventure of a lifetime as the old Fairy Detective Agency comes back to life. It is up to Emily to reopen the shop, and recall the fairies to duty. Together they must embark on their first mystery and do battle with their great fairy-snatching enemy, Harpella.