In pre-Civil War America a gunslinger and a priest stalk from coast to coast fighting monsters, exorcising demons, and secretly shaping the history of the nation. Posing as Union soldiers in the Texas territory, Tom and Weston takes possession of an ancient artifact that destroyed an entire town only to be ordered into a nearby fort by the approach of the Mexican army. Once the fort is surrounded they discover that it has been raised from the dead by a demon that possessed the general. With only a small detachment of soldiers to defend the fort and the artifact Tom and Weston must withstand a relentless siege of undead, and escape with the artifact without being eaten alive.