The Seeing Stone (2) (The Spiderwick Chronicles)

Thanks to the mysterious field guide left behind by their long-lost great-great-uncle, Arthur Spiderwick, life for the Grace kids—Jared, Simon, and Mallory—is beyond weird. When Simon goes missing, Jared is convinced creatures from the faerie world have something to do with it. Mallory is not convinced. That is, until she and Jared contend with a band of menacing, marauding goblins. Simon is clearly in danger, and it’s up to Mallory and Simon to save him before it’s too late.