Roy Rogers, troubleshooter for the U.S. border patrol, receives orders to prevent the spread of hoof-and-mouth disease from Mexico into the United States. At the border fence, Roy meets his friend Lopez, who has been transferred from Mexico to assist him. With them is Lopez' young son Pancho, who notices signs of a bear, a possible hoof-and-mouth carrier, that has climbed the fence. Roy's trained dog Bullet picks up the bear's trail, which doubles back toward Pancho. Roy kills the bear, but Pancho has been scratched, so Roy takes him to the doctor. Lopez, meanwhile, heads for the patrol camp at Borrasco, where sandstorms are heavy and frequent. On his way, he encounters Ward Sloan and Lucky Grillo, who are planning to herd cattle from Mexico over the border as soon as the winds pile sand against the fence to form a temporary bridge. By altering their cattle brands, they sell Lucky's Mexican herd as Sloan's at the higher, U.S. price. The profit far exceeds their other schemes, but they worry that the recent uproar over hoof-and-mouth disease could complicate their plans. While attempting to arrest them, Lopez recognizes Lucky as the murderer Jim Bradford. Sloan kills Lopez, and he and Lucky leave the body for the storm to bury. Later Sloan and one of Lucky's men, Tony, attend Col. Wells's Cattlemen's Association meeting in Capital City about the hoof-and-mouth problem. Concerned that their herds will be confiscated by the government if any diseased cattle are found, the ranchers are demanding action, and the colonel assures them Roy is working on the problem. Cathy Marsh, a journalist reporting on the disease, remains after the meeting and eavesdrops as the colonel gives Roy, who has arrived for an appointment, three weeks to find answers. She has arranged with Elena Madera of the Borrasco freight office to use desk space there, and when she arrives from Capital City, Elena's assistant and would-be wooer, Pinky, takes a photograph of Cathy and inadvertently captures Sloan and Tony talking in the background. The two outlaws fear the picture might later incriminate them, so they fight Pinky to break the photographic plate and destroy the evidence. Roy jumps in to assist Pinky, but gets blamed by Elena for the camera's damage. Ignoring Roy's advice to wait for the real story, Cathy prints a sensationalized story that ends with Roy's involvement in a street brawl. In the meantime, Sloan reports to Lucky that an expert tracker has been assigned to the hoof-and-mouth problem. Lucky and Sloan decide to make one big transfer of cattle, then lay low for a while. Near the border fence, Roy and Pat, another patrolman, are looking for Lopez, and see Tony and two others recovering Lopez' body. During the fight, Pat shoots one man and Roy captures Tony, but the third man gets away. Later, Cathy wants to write another news story, but again Roy begs her to wait until Pancho can be told about his father's death. Pancho's anxiety has turned into nightmares, and he goes out with Bullet to search for his father. Lucky, on his way to see Sloan, finds Pancho and takes him as hostage to Sloan's ranch, where the men are leaving for the border to bring in the herd. At the jail, Pinky recognizes Tony from the fight over the camera, and he and Roy see the link to Sloan when they print the photograph. They ride to Sloan's ranch and defeat the few remaining men, but in the skirmish Sloan is killed. Pancho and Bullet are sent for help, but are pursued by Tony, who has been freed by Cathy and Elena in response to a hostage note from Lucky and Sloan requesting a trade of Tony for Pancho. Tony intends to kill Pancho, but is himself killed by a bear. Pancho and Bullet find Pat, who rounds up the patrolmen. They arrive at the border in time to help Roy and Pinky arrest the smugglers and reroute the cattle to Mexico. Afterward, Roy and his cohorts gather at the camp. Cathy, who has just made her biggest scoop ever, agrees to get Pancho to school, and he promises to study hard, while Roy rides off to his new assignment.
A 7 May 1951 Hollywood Reporter news item reports that Jimmy Bryant, George Bamby, Bud Dooley, Michael Barton and Darol Rice were cast in the production. According to a January 1951 Hollywood Reporter news item, they were members of the singing group, the Roy Rogers Riders. Pals of the Golden West marked Roy Rogers' final film with Republic, following an association that began in 1935. Rogers made over eighty films for the studio.
