Longarm needs to even the score with some ladies of the evening. When Deputy U.S. Marshal Custis Long's boss, Billy Vail, sends him to the town of Salt Springs in New Mexico Territory to investigate a possibly crooked lawman, he needs a good cover. Whiskey salesman, wandering gambler, and doctor specializing in female complaints are all ruled out. Land speculator should be safe, Billy decides.   But Longarm still manages to get himself into some trouble when he books a room in the town's only hotel, which also happens to be a brothel. Longarm quickly learns there's more going on behind closed doors than good times. Some of the ladies of the world's oldest profession may be moonlighting...as stagecoach robbers.