Outside Sam Hall's Last Chance Saloon, cattle buyer "Trigger" Tom Hunter saves the life of Stub Macey and then hires him to help purchase cattle in the nearby Blue Mountains, an area plagued by murderous renegades and outlaws. In the mountains, sheriff and town boss Pop Slater warns rancher Nord Jergenson that his cattle may only be sold to Mose Jeckyl the outlaws' chief, and reminds him that he is wanted by the law for having killed a man. At a narrow mountain pass, Jeckyl's guard fires at Stub as he tries to enter the valley, but Tom pursues and captures the assailant. Jeckyl rides up and introduces himself as the sheriff, taking charge of his guard and giving Tom and Stub incorrect directions to the Jergenson ranch. Stub, knowing the way himself, is suspicious. After Jeckyl warns Jergenson that two strangers, probably marshals, have entered the region and are heading for his ranch, Jergenson pays the outlaw to keep quiet. Scarface, a spy for Slater, gives a similar warning to the townfolk, who then snub Tom and Stub. Slater's rancher son Sam and his friend, Cal, however, are not outlaws and want a higher price for their herds than Jeckyl will pay, so they join Tom. Tom also wins the confidence of Jergenson and his niece Dorothy. Despite Slater's blackmail, Jergenson wants to sell his cattle to Tom so that Dorothy may receive a good education. Although Slater turns Jergenson's cowpokes against him, and they refuse to help round up the cattle, Tom is not deterred. At the same time, Cal and Sam gather their own herds. As all the cattle begin to head through the pass, Dorothy alerts Tom to a gunfight raging between Jergenson and Slater. Jergenson shoots Slater, and Tom arrives in time to prevent Scarface from firing at Jergenson in retaliation. While dying, Slater confesses to Sam and warns him that Jeckyl is preparing to dynamite the pass. As the fuse burns, Tom fights with Scarface and Jeckyl, who falls to his death. Tom escapes in time to rescue Dorothy from the explosion. When Jergenson sees Tom capture Scarface, the man he thought he had killed, he realizes that Jeckyl, Slater and Scarface conspired to intimidate him by making him believe he was a murderer. After the outlaws are apprehended, Jergenson, Sam and Stub complete the round-up, while Dorothy and Tom kiss.