Lucinda's Secret (Spiderwick Chronicles Series #3)

Things at the Spiderwick estate are getting completely out of hand. As if being attacked by goblins and almost eaten by a bridge troll wasn't enough, now the house boggart, Thimbletack, is out to get Jared. Simon has a very hungry griffin recuperating in the carriage house. And Mallory is convinced that the only way to stop the madness is to chuck the Guide. Fortunately for Jared, that's not an option. With all kinds of creatures after them, the Guide is the only protection the Grace kids have. If he could just figure out why all of Faerie wants it. There's only one person who can help solve this mystery -- their crazy old aunt Lucinda.