Fury of the Demon. Demon Novels, Book Six

Demon summoner Kara Gillian bears the scars of Rhyzkahl's treachery, but she refuses to let them slow her down. She and the demonic lord Mzatal have not rested in their efforts to recover Idris-Mzatal's summoner protégé who was kidnapped by enemy lords-but now their search has brought them back to Earth. With the help of FBI agents Ryan Kristoff and Zack Garner, they begin to track down summoners who are working with Rhyzkahl.
However, Kara knows Ryan's true identity, and questions of loyalty threaten to tear apart this group of allies. When Kara intervenes to help a brilliant young computer expert and his bodyguard after an accidental shooting, she quickly learns that Rhyzkahl's machinations run deeper than she could have ever imagined. The search for Idris takes on a desperate edge as their enemies increase in number, and Kara realizes that an old homicide case may hold the key to their success-or their doom.
With the very fabric of the universe at stake, Kara must rely on her skills, wit, and luck to save her friends and her world, yet ancient vows will have to be broken if she is to have any hope. But the price of breaking those vows may be her own blood. Fury of the Demon is the exciting sixth installment of the Kara Gillian series.