The Grace family moves from Brooklyn, New York, to their ancestral home in Henson, Michigan, the Spiderwick Estate. Helen makes the move with her 15-year-old fraternal twin boys, Jared and Simon, and her older daughter, Mallory. Shortly after moving to the Spiderwick Estate Jared discovers a boggart and realizes that magical creatures are real! The only one to believe him is his great-aunt Lucinda who implores Jared to find the pages of her father's field guide to magical creatures and protect them from the murderous Ogre, Mulgarath.