Lucinda's been carted off to a sanitarium, claiming that strange things happened there and was put away for her troubles. For some reason she has stocked up on honey, salt and tomato sauce. So now the Spiderwick mansion is home to Helen and her three children. And there's a lot of life in the Spiderwick mansion.

Simon, the bookish twin, isn't any more curious about this than Mom or sister Mallory (Sarah Bolger). But Jared, the twin with anger issues, is intrigued. The Graces are in the house for a hot minute when a tiny, elflike creature named Thimbletack, who lives in the mansion's walls and guards Spiderwick's book, reveals himself to Jared.

This vengeful "boggart" (the voice of Martin Short) turns into rat-size, foppish ``brownie''. For the last 80 years, Thimbletack has protected a field guide to magical creatures assembled by the Grace kids' Great Uncle Arthur Spiderwick (David Strathairn), who unlocked every secret before a silken cloud of fairies whisked him away forever. This book will Bring About the End of the World if it falls into the hands of Mulgarath, a truly evil ogre (voiced by Nick Nolte).