Deputy Federal Marshal Frio Buchanan rides into the dusty outpost of Saguaro Gulch to search for a missing senator's nephew. He finds a town under the thumb of the Gibson Brothers and their gang of ruthless enforcers.

As Frio investigates, he stumbles across a secret: a monster thriving in the dark, waiting for its time in the light. It takes all of his wits-and a lot of gunplay-to escape death.

But the danger still lurks, threatening everyone not allied with the Gibsons.

Can Frio save Saguaro Gulch from the creature hidden in the old mine?