Bud Wren and Mabel Garden are sweethearts in the town of Red Dog. Numerous mail robberies occur, but there seems to be no clue to the robber. The chief of the Secret Service wires James Garden, sheriff and postmaster of Red Dog, that he is sending him a man to unravel the mystery of the postoffice thefts. The Sheriff, Bud Wren and Pratt, another cowboy, are engaged in playing cards in Thirsty Fish bar when a stranger enters. He watches the game in a casual manner, when Pratt and Wren, who with the sheriff have been losing heavily, get into a fight over the game. The stranger assists the sheriff to separate them. Wren, rather ugly, goes out, swearing vengeance on Pratt, and goes to the latter’s cabin, falls asleep, and waits for Pratt to appear. Pratt, the sheriff and the stranger meanwhile play cards. The sheriff loses, while Pratt gathering up his winnings in a bag, invites them to a drink. After buying the drink, Pratt leaves for his home. The stranger noticing a medal pinned on the sheriff is informed by him that it was received for being the best shot in the country. Five hours later old man Simpson, a trapper, sees Wren leaving Pratt’s shack. Next morning a cowboy discovers Pratt dead on the floor, and Wren’s gun beside him, and informs the sheriff. The stranger sees the sheriff rifling letters. Old man Simpson is talking to the sheriff as the cowboy tells of finding Pratt. Simpson tells of seeing Wren come from the shack. The sheriff calls a posse and they ride off followed by the stranger. At the shack the sheriff shows all Wren’s gun found at Pratt’s side. Mabel, riding up, hears them accuse Wren of the murder and suggest lynching. She rides off to get cowboy friends to stop the lynching. Wren wakes up on the side of the road in a drunken stupor. The party find him there. Meantime the stranger finds clasped in Pratt’s hand a medal, which he immediately recognizes as the one the sheriff had worn. He mounts his horse and rides after the posse. On the way he meets Mabel Garden and the cowboys and together they ride to where the sheriff is about to lynch Wren. The stranger accuses the sheriff and shows the medal as proof and also pulls from his pockets some letters which the sheriff and postmaster has stolen. He shows his Secret Service badge and the sheriff is taken away. Wren puts his arm around the girl he loves and the picture fades out.