Retired professor of entomology Alonzo Larson and his daughter Anne have come West from New England to settle at "The Paradise Ranch," which they bought sight unseen. The ranch is adjacent to Hopalong Cassidy's, but the buildings and land are in very poor condition and the professor realizes that he has been tricked by crooked land agent Bentley. The professor turns out to be an old acquaintance of Hoppy's pal California Carlson, and Hoppy, Lucky Jenkins and California decide to try to help him. Hoppy thinks that there may be silver on the land and asks Bentley to confirm that the professor does in fact own the ranch. While California helps the professor catch butterflies, Hoppy goes to see banker Gerald Waite and tells him about the silver. Unknown to Hoppy, Waite is in cahoots with Bentley and tells him to nullify the sale. Bentley rushes out to the ranch and is about to receive the deed back from an unsuspecting Alonzo when Hoppy arrives and stops the negotiation. In order to start mining operations, Hoppy arranges for the professor to borrow money against the property from Waite's bank, with the first payment falling due in thirty days. However, as mining progresses, there are several accidents, engineered by Bentley and Waite, and the hired hands threaten to quit. Radley, a representative of a smelting company, contracts for the mine's entire output. Later, Buck and Sam, two of Bentley's henchmen who are working at the mine, report to him that ore shipments will begin within a week. Waite suggests that a cave-in at the mine would put an end to the deal. Meanwhile, Hoppy signs a contract promising to deliver the ore on time or default on the smelting company's loan guarantee. One night, Buck and Sam arrive at the mine with a case of dynamite but encounter California and the professor trying to catch an owl. They slug the professor and place him in the mine. As Hoppy comes to look for the professor, Buck and Sam light the fuse. Hoppy shoots Buck and chases Sam into the mine, where they have a gunfight, but Hoppy manages to rescue the professor just before the dynamite explodes. The next day, Hoppy tells Waite that the explosion was a great help as it opened up a new silver vein. Deal Marden, another Bentley henchman, joins Hoppy's outfit, claiming that he has reformed. Just before the first shipment is to leave, Marden heads back to town to tip off Bentley. Hoppy follows Marden and after he sees him reporting to Bentley and Waite, is discovered but escapes. The next morning, as the three wagons leave with the ore, Bentley and his gang prepare an ambush. The attack backfires, however, as one of the wagons contains several of Hoppy's men armed with rifles. Later, Bentley attempts to block the trail with boulders, but Hoppy and Lucky surprise him and a gunfight ensues. Bentley escapes but Hoppy tracks him to Waite's office and "invites" them both to accompany him to the smelter to return the agent's loan guarantee. After California gets the wagons to the smelter in time, Hoppy tells Waite to hand over the cash so that the professor can pay off his note. Hoppy then gives Bentley, Waite and their men twenty-four hours to leave the area. The professor and Anne are now prosperous and Lucky begins courting Anne.