1864 looks promising for Azariah Martin. He has a new title, a new office, and the company of his fiancée, the beautiful and headstrong Mary Foster.

But he leaves it all behind when he's sent on a top-secret operation to the uncharted West to track down a gang of British spies, codenamed Black Birds, who are working with the Sioux and Cheyenne to sabotage construction of the transcontinental railroad.

Azariah quickly learns that hunting spies in the wild West is a dangerous game, one he'd better learn to play fast if he's going to survive.