Unseen

Author: Rachel Caine
Publication Date: 1 February 2011
Publisher: Roc US

After Cassiel and Warden Luis Rocha rescue an adept child from a maniacal Djinn, they realize two things: the girl is already manifesting an incredible amount of power, and her kidnapping was not an isolated incident. 
This Djinn-aided by her devoted followers-is capturing children all over the world, and indoctrinating them so she can use their strength for herself. With no other options, Cassiel infiltrates the Djinn's organization-because if Cassiel cannot stop the Djinn's apocalyptic designs, all of humanity may be destroyed.