Shemp is suffering from an enlarged vein in his leg, and fears that it will lead to amputation. His doctor (Vernon Dent), however, advises that a few weeks in the old west will cure him. Upon arrival in a somewhat lawless town, the boys befriend the ruthless Doc Barker (Jack Norman). Barker listens to Shemp's story about his bad leg, mistaking "the biggest vein you ever saw" for a gold-bearing vein worth millions. The Stooges take a liking to Barker, but are later informed by the beautiful Nell (Christine McIntyre) that he is an outlaw who is holding the Arizona Kid (Jock Mahoney) hostage in the basement of the saloon.
Thr boys hatch a plan to obtain the prison cell keys from Barker's coat. Shemp joins the outlaw in a game of Poker, while Moe and Larry prepare beverages for the card players. The two find every possible deadly chemical they can to add to their volatile drink, from Old Homicide to paint (plus paint remover). They also prepare a Sarsaparilla for Shemp to make sure their pal does not indulge in the suicidal drink. Barker downs the concoction, and screams for water. Shemp grabs a nearby fire hose and sprays the entire gang, soaking them. Moe and Larry quickly grab Barker's coat (claiming he will catch pneumonia) and get the cell keys to Nell, who frees the Arizona Kid. When Barker sees what has happened, he throws Larry in the cell with plans to kill him at sunrise.
Seeing how desperate the situation has become, the Arizona Kid goes to retrieve the United States Cavalry while Moe and Shemp attempt to free Larry using every tool they can find. Eventually, they spring Larry and defeat Barker and his gang.