It's the early days of the Mexican revolution. J. T. Latham is about to be killed by a Yuma Prison gang when an old nemesis, Deputy Del Buchman, intervenes. Latham will get a pardon if he uses his knowledge of the area and his experience with the Yaqui to guide Buchman's posse deep into the Sonoran desert to rescue rich man's kidnapped wife and children. The guerrilla general responsible wants machine guns for their safe return, but there is more to the ransom than guns. The trail is bounded with danger, treachery and the question of mercy as Latham tries to outmaneuver the next chess move of his adversaries. Getting out of prison was easy, now Latham has to get out of the desert alive.