When Gene and Pat go to take a drink at a waterhole, they find an empty bottle of poision along the banks. Gene then runs into his old Indian friend, Chief Tejon, who explains that the Central Valley Railroad are refusing to comply with their contract. Gene and Chief Tejon ride to the railroad camp to investigate. Gene has no luck, and rides to Willow Gap, where he finds the contract hidden in the office of the chief engineer, Craig. Pat discovers a connection between Craig's sister, and an assayer, who has bottles of poison in his office.