No Quest For The Wicked (Enchanted, Inc. #6)

A Questing We Will Go
Now that the Magic, Spells, and Illusions, Inc. team has defeated the nefarious Spellworks, the only "competition" in town, Katie Chandler doesn't have much to do as director of marketing, and she's starting to question her role at MSI. Her boyfriend Owen Palmer, on the other hand, is in hog heaven, translating an ancient and powerful magical manuscript. 
But then he finds that the cryptic text describing the location of an enchanted gem known as the Eye of the Moon has radically changed. This deadly stone gives its holder enhanced power over others and a craving for more power. It once caused a terrible war before it was safely hidden and then lost - and now it seems to be in New York and set in an elven brooch that renders its wearer invulnerable. Whoever has this brooch could take over the world.
Katie and Owen must find it before anyone else does, and they're not the only ones searching. They'll need all the help they can get, including Katie's visiting grandmother. But who can they trust when their allies fall under its spell? Not to mention the new enemies who are deadlier than anything they've faced before.