The Named book by Marianne Curley

Ethan lives a secret life as a Guardian of the Named. Under the guidance of Arkarian, his mentor, and with the help of Isabel, his unlikely but highly capable apprentice, Ethan has become a valued member of this other-worldly corps. As the only defense against the evil Order of Chaos, the Named travel through time to prevent the Order from altering history and thereby gaining power in the present and the future. As the threat from the Order intensifies, secrets of the past are revealed and villains and heroes are exposed. This gripping fantasy is set in modern times, but is infused with intrigue from the past, super-natural characters and surprising plot twists. Curley has written a winner through to the end. Published By Bloomsbury USA Childrens on 2002-10-04