In 1928, Arthur Spiderwick writes a field guide about the many fairies he has encountered. After finishing the Book, he hides it away for fear of Mulgarath, a shapeshifting ogre who plans to use the Book's secrets for evil. Eighty years later, recently divorced Helen Grace inherits and moves into the abandoned Spiderwick estate with her children, 13-year-old daughter Mallory and 12-year-old twin sons Jared and Simon. Jared is angry about the move and would rather live with his father in New York. After uncovering a hidden dumbwaiter, Jared discovers Arthur's study where he finds the Field Guide. When Jared explains his discovery of the Book and the existence of magical creatures, his family does not believe him. The next morning, Jared meets a brownie named Thimbletack, who is initially angry with Jared for having opened the book that he needed to protect from Mulgarath. Jared placates him with crackers and honey, and Thimbletack gives Jared a holed stone that allows Jared to see the normally invisible fairies by looking through it.