Jared, though, begins to notice unusual things happening around the magical house, and begins to investigate. Ignoring the warning of a house "brownie,” Thimbletack (Martin Short), an enchanted creature who lives in the walls of the manor, he comes upon a strange and potentially dangerous book written by Uncle Arthur, Arthur Spiderwick's Field Guide to the Fantastical World Around You. Once opened, the book reveals – and unleashes – a world surrounding the Spiderwick Estate inhabited by some odd, wonderful - and scary – beings: a wily but friendly hobgoblin named Hogsqueal (Seth Rogen), a pack of dangerous goblins and the beautiful and mysterious fairies and sprites. Only those who look through a magical "seeing stone” or have a slovenly hobgoblin spit in their eye – the gooey fate of each of the children – can see these creatures.

But it is the crafty, evil ogre, Mulgarath (Nick Nolte), who poses the most ominous threat. The children begin to realize that the Field Guide is not merely a work of their uncle's imagination, but the key to all the fabulous beings they encounter, offering unbelievable power to anyone who understands its secrets. And Mulgarath will stop at nothing to get his hands on it!