U. S. Marshals Nevada Jack McKenzie and Sandy Hopkins come to Teton at the request of Dan Broderick to try to find out why and by whom the ore from the mine is being hi-jacked. When Broderick decides to deliver his own ore, the assayer tells him it is worthless. He is about to sell the mine to the saloon owner but Nevada asks him to hold off for a few days. Nevada and Sandy discover that the ore is being switched en route to the assayer but manage to get a good shipment through. The saloon owner and his gang alter the reports but the two Marshals take the assayer to the mine for an on-the-spot analysis. They are almost trapped in an explosion set by the crooks, but escape and round up the gang.