At the All-American Canal, along the California-Mexico border, hundreds of Mexican farm workers, known as "braceros," wait to make their daily crossing into California. Some of the workers cross into the United States legally, while many others enter illegally. Many of the workers are robbed and sometimes stabbed by bandits, who ambush the braceros on their way home. Hoping to end the often deadly ambushes, the Mexican and American governments send officials to meet and discuss a possible solution to the problem. Soon after immigration investigators Pablo Rodriguez, a Mexican, and Jack Bearnes, an American, are assigned to the case by their respective countries, Pablo volunteers to disguise himself as a bracero and investigate the well-organized bandit operation. As part of their plan, Jack will follow Pablo and monitor all the contacts he makes on the Mexican side. After finding Owen Parkson, an American bracero broker posing as a rancher, Pablo tries to win his trust by telling him that he is running from the police. Though reluctant to believe Pablo's story, Parkson agrees to transport him across the border, and directs him to a truck filled with farm workers. Jack, meanwhile, loses his trail and falls into the hands of Parkson, who holds him prisoner in his camp, demanding the "stolen" immigration papers that Jack has offered him. Pablo sees Jack there, but does not offer him help for fear that he might expose their identities. Parkson eventually discovers the trap when he intercepts a telegram that Jack has sent to the immigration authorities. After ordering Jack killed, Parkson, realizing that he is the target of an investigation and is about to be arrested, decides to hide the evidence of his operation by sending the braceros back to Mexico. Pablo, who is among the men who are to be sent back, spurs the braceros to riot, and a bloody fight ensues. Parkson and many of his henchmen are killed in the battle, but a border patrol unit arrives in time to bring order and arrest the remaining crooks.