Crash, Dusty and Alibi, "The Range Busters," witness three gunmen attack an unarmed man in a wagon. They ride to his rescue, but arrive too late, and the man dies in Crash's arms, imploring him to care for his baby and warning him to watch out for a man named Amos. Fearful that they will be accused of the man's murder, the Range Busters decide to investigate for themselves. Meanwhile, Marion Horner, the murdered man's sister, finds her brother's dead body in his wagon and worries about the missing baby, prompting her friend Jim Moreland to organize a posse to search for the child. Unknown to Marion, Moreland arranged for her brother's murder because Horner had appointed him executor for his baby son. With Horner out of the way, Moreland would be free to fill a $50,000 contract for the gravel found on the Horner ranch, a contract that Horner opposed. Moreland orders his henchman Kirk to find the three men who rescued the baby and frame them for Horner's murder. Meanwhile, Dusty and Crash walk into Moreland's trap when they visit Amos Hardy, who is working with Moreland. After a brawl with Kirk and his men at the saloon, the pair ride out to Horner's Bar H ranch, where they meet Marion, who tells them of Hardy's offer to buy the ranch and Moreland's job as executor of her brother's estate. Learning that the Range Busters have come to Marion's aid, Moreland abducts her to his cabin in Mesquite Canyon. While Marion is held prisoner, Dusty and Crash break into Moreland's office and find the gravel contract, thus establishing Moreland's motive for murder. Deciding to force a showdown, the Range Busters lead Moreland, his men, the sheriff and his posse on a chase to Mesquite Canyon where they produce the contract that proves Moreland's guilt. After Hardy confesses that he and Moreland arranged for Horner's murder, the sheriff arrests them and frees Marion and the Range Busters ride away, knowing that their job is done.