Rose Campion and the Curse of the Doomstone (Rose Campion, Bk. 2)

Business has never been better for Campion's Palace of Variety and Wonders - and the music hall is about to open its doors to its biggest act yet: the Illustrious Gandini, the stage magician known as the Great Wizard of the North. But when the Doomstone Diamond - a priceless jewel with a disturbing history - is stolen during one of Gandini's performances, Campion's finds itself under threat once more, and Rose Campion and her friends will need all their wits about them to find the thief and uncover the secrets of the magician's mysterious past...