After Mexican American cowboys The Cisco Kid and Pancho are falsely accused of a series of stage holdups, which are actually being perpetrated by two outlaws disguised to look like them, they escape from a sheriff and his posse and arrive in San Lorenzo, California. When Pancho receives a letter from someone claiming to be his ailing grandmother and pleading with him to come to Cactus Wells for a visit, Pancho tells Cisco that his grandmother is dead. They decide to go to Cactus Wells anyway to investigate the strange letter, but while riding down the street, they are shot at by a rancher named Thomas McCarger, who has been informed that Cisco murdered his brother. When bystander Nora Malloy sees McCarger draw his gun, she tries to grab it out of his hand. Later, Nora takes the stage to Cactus Wells, where she is to wed her fiancé, Jerry Todd. Cisco and Pancho, meanwhile, visit McCarger, who shows them a letter from Sheriff Ed Marlowe. The letter states that Cisco shot McCarger's brother during a stage holdup, but Cisco explains that he has never been to Cactus Wells, then vows to go there to search for the real murderer. On their way, Cisco and Pancho see Rusty and Kansas, their impersonators, attacking a stagecoach. The outlaws shoot the driver and the guard before holding up the stage and escaping. Cisco aids the stage driver, who turns out to be Jerry, and he and Pancho take him to Nora's. When the sheriff and deputies arrive at Nora's to question them, Cisco and Pancho hide in the kitchen. Nora then grabs her gun and orders the lawmen to leave. Then, Rusty and Kansas burst in and lock the sheriff inside the cell, kidnap Cisco and Pancho and take them to the gang's hideout inside a cave in the mountains. After Cisco and Pancho fight with their captors and escape, Cisco holds up the stage and steals the express box. A short time later, Rusty and Kansas don their disguises and rob the stage, demanding the box. When the exasperated driver explains that he already gave it to them, the outlaws realize that Cisco and Pancho must have escaped. Cisco and Pancho break back into jail, release the sheriff and tell him about the impostors. That evening, at the newspaper office of the gang's leader, editor Ross, a rock is thrown through the window with the following note attached: "This is fair warning. I will come for the loot in your office safe before daylight. The Cisco Kid." Ross opens the safe to check on the loot, just as Cisco and the sheriff are arriving. After the rest of the outlaws show up and are arrested, Cisco asks the sheriff to send a letter to McCarger identifying his brother's murderer as Ross. Later, Cisco and Pancho accept the sheriff's thanks, then say farewell.