United States Marshal Boone Crowe of Wyoming Territory seems no closer to a hopeful retirement when he stumbles upon the ghastly scene of a massacred family. Saddled with a prisoner he doesn't want, and an orphaned girl who has survived the carnage, he must turn his trail in pursuit of those responsible. A wandering family of cutthroats, drifting up from the south, has laid waste to all in their path. Fueled by whisky and a lust for cruelty, the deadly Mohegan clan scatter like ripples on the water, leaving Boone Crowe too many trails to follow. Forced to enlist the aid of his prisoner-horse-trader and sharpshooter, Tugs Bigelow-they head out to track down the killers. Complicating matters is a young, rash Texas Ranger, on his own killing mission, out to avenge the murder of his father. Peppered with an array of hard-bitten characters, Showdown in the Bear Grass pits the sturdy lawman in a race against time. Carrying justice in his Colt and Henry rifle, the aging marshal, steered by his own rage, sets out to spare the Wyoming range from being washed in more blood.