In the previous book, the Grace kids encountered a trio of elves deep in the forest. Now they're dealing with dwarves in "The Ironwood Tree," the fourth and next-to-last of the Spiderwick Chronicles -- and Holly Black and Tony DiTerlizzi do a solid job adding menace to a fantasy species that usually isn't too spooky. Plus, a great lead-in to the grand finale. 
 The Grace family arrives at the high school to watch Mallory's fencing match, but during one match Jared notices a strange girl rifling through his sister's bag. And even worse, a strange doppelganger of Jared appears and menaces him, hoping to find the Guide. Finally, worst of all -- Mallory vanishes, leaving behind only her fencing medal and a stone with the word TRADE carved into it. 
 While their mother freaks out about what a "problem child" Jared is, the twins go rushing off to an abandoned quarry nearby, and soon find their way into an underground civilization populated by dwarves. These master craftsmen have taken Mallory, and they also have some rather unpleasant (and unrealistic!) plans for the upper world. 
 "The Ironwood Tree" contains some of the most atmospheric, fantastical scenes in the entire Spiderwick Chronicles series, as Holly Black introduces us to an eerie underground city with silver-leaved ironwood trees, statues and stalactites, silver and golden animals and platinum flowers. In fact, I was left wishing that we had spent a little more time down there. 
 Holly Black's prose is really beautiful here, especially when she describes the underground world of the dwarves ("Glowing fungi covered the walls in patches, illuminating the faces of three small men with skin as gray as stone"), and she gives the dwarves a menacing edge that definitely sets them apart from Disney's jolly harmless little men. And Tony DiTerlizzi's delicate pen-and-ink drawings are simply lovely, especially his depictions of Mallory in the glass case. 
 However, there appear to be some obstacles for the twins on the home front, since a faerie successfully makes Jared look like a knife-wielding psycho, and their mom is bleating about how she can't handle him. The only downside is that Mallory plays the typical damsel-in-distress role; it would have been nice to see her kicking some dwarven butt. 
 "The Ironwood Tree" successfully pulls our preteen heroes into a strange underground world, and adds a coldly exquisite edge to this series. And the door is open for the grand finale.