Yaqui fighters surround a wagon train, so Jim Harvey (Audie Murphy), the man guiding the pioneers, steps out to negotiate. But they ignore his pleas and overrun the wagons, leaving him for dead. He manages to escape to the nearest town, but there the law accuses him of deserting the settlers. The townspeople try to lynch him, so he flees to a ranch owned by kindly Nick (Roy Roberts), who lends Jim a trusty horse named Tumbleweed that may just be fast enough to save the day.