When Mallory and Jared attempt to rescue Simon from goblins, they use a magical stone which enables them to see things that are normally invisible.

First a pack of goblins snatched Simon. Then a band of elves tried to entrap Jared. Why is the entire faerie world so eager to get their hands on Authur Spiderwick's Guide? To make things even worse, someone is running around pretending to be Jared at school, Mallory has disappeared, and something in the water is killing off the plants and animals. Will the Grace kids be left alone, now that the Guide has mysteriously vanished? Don't count on it.