Danger lurks in the shadows and no one knows that better than those who have pledged themselves to keep the world safe from dark and increasingly deadly forces, the Knights Templar.

Left for dead in the wake of an attack by a fallen angel, Cade Williams now commands the Echo Team, one of six elite combat units in the Templar hierarchy. But Cade is no ordinary soldier; his encounter with the supernatural left him with a thirst for vengeance for the death of his wife, Gabrielle. That, and supernatural abilities of his own-- earning him the nickname the Heretic among his faith-driven brethren.

When a group of necromancers raid a Templar stronghold and steal a powerful relic, Cade and the Echo Team spring into action to prevent the unimaginable consequences. But the mission goes awry when Cade discovers that the power behind the necromancers is none other than the Adversary, the angel of darkness that tried to kill him years before. Will Cade sacrifice the mission, and possibly the lives of his men, for a final chance at vengeance?