In the 1870s, on the lawless border between Texas and Mexico, the oldest law enforcement agency in America was born: the Texas Rangers, who became an enduring symbol of honor and valor. It was a time when Mexican banditos were raiding the border, Indian tribes were battling for their traditional lands and settlers were pushing west by the thousands lured by the promise of a new life. The rustic country along the Rio Grande River was in chaos as gangs raided farms and family ranches, then took refuge south of the river, beyond the reach of local sheriffs and the US Army. Only the Texas Rangers had a chance to turn the tide and bring justice back to the people. One legendary man, Leander McNelly, is chosen to lead a band of unlikely heroes- many of them young, inexperienced men -in a battle with the renegade outlaws who made the Texas frontier the most dangerous place in America.