The Restorer's Son by Sharon Hinck

Book 2 of Sword of Lyric

Summary: 

Chosen to save a people. Called to serve an enemy.

lunged again into the gray world of Lyric and Hazor, Susan and Mark search frantically for their teenage son, Jake, as all signs hint that a trusted ally has betrayed them. Assassins, political intrigue, false leads, and near misses beset their path, which will lead them into the dark prisons of Hazor before the One's purpose is revealed.

Cast out by those he trusts and preferring to cross swords with the One rather than yield to His will, Kieran flees to enemy Hazor, only to find that the One knows no borders. Pursued by his calling, Kieran finds a boy without a home, a king with burning questions, and a nation torn by darkness. As he embraces the tasks the One has set before him, this new Restorer learns that the One requires his all-perhaps even his life.

Opening Lines: 

"Hills of Hazor take you," I swore for at least the tenth time since first light. My sword hacked at thick underbrush, but when I shouldered my way forward, a twig snapped back at my face. I cursed the day I'd met the last Restorer. It was because of her that I was battling through this forsaken forest below Cauldron Falls. My blade deserved a more substantial enemy.