It starts with the most horrific act of terrorism ever committed on American soil. Only one man can stop them. Code named Devlin, he exists only in the blackest shadows of the United States government -- operating off the grid as the NSA's top agent. He's their most lethal weapon . . . and their most secret. But someone is trying to draw him out into the open by putting America's citizens in the crosshairs -- until they get what they want.