While robbing the Gilda stagecoach, The Cisco Kid, along with his friend Pancho, meets Ellen Roth, a registered nurse. Cisco abducts Ellen, knowing that she has been falsely accused of murdering her wealthy patient and benefactress, Mrs. Prescott. With the posse out looking for them, Cisco and Pancho then go into Gilda, where Cisco forces Pancho to return their booty to the empty sheriff's office. Afterward, Cisco waits at the post office to discover the owner of box seventeen, an address to which Mrs. Prescott had sent many letters. After Will Hastings, a saloon owner, removes a letter from the postal box, Cisco steals it and takes it to Ellen, who has sought sanctuary at the local mission. Though she has no further understanding of the letter than he, Ellen tells Cisco that Mrs. Prescott was administered a lethal overdose of sleeping pills by a "Dr. Wills," who claimed to be the new assistant of Mrs. Prescott's regular physician. As the letter has a reference to "Dolores," Cisco and Pancho go back into town to hunt for Dolores, who turns out to be a singer in Hastings' saloon. Dolores tells Cisco that Hastings recently returned to Gilda after a six-month absence and told her that he was about to come into "a great deal of money." After a brief fight with Hastings, Cisco is forced to make a hasty retreat from the saloon when Sheriff Clem Petty arrives. Later, while the sheriff and his posse chase after Pancho, Cisco returns to town and confronts Hastings, who, he has learned, was Prescott's estranged nephew and next of kin. Cisco offers to turn Ellen over to Hastings for $10,000, and the crooked saloon owner quickly agrees to the bandit's terms, knowing that, upon Ellen's arrest and conviction, he will inherit his aunt's estate. After Ellen's arrest, Cisco and Pancho force the local printer to run a fake newspaper story, stating that Ellen has been exonerated and Tom Wills, alias "Dr. Wills," has been arrested for Mrs. Prescott's murder by the Denver police. Assuming that Ellen's testimony is the only evidence against Wills, Cisco offers to kill the nurse for Hastings. While Cisco fakes Ellen's murder, Wills arrives in town. The phony physician soon falls into Cisco's trap, and is taken unconscious to the mission. In the meantime, Hastings discovers Cisco's deception, but he, too, is captured by the bandit. When Wills awakens, he finds himself under the care of Ellen and confesses all, as Cisco, Pancho, Hastings and Sheriff Petty eavesdrop. Hastings and Wills are arrested for the murder of Mrs. Prescott, and Ellen offers her gratitude to Cisco.