The Vanishing Riders.

Sheriff Bill Jones, in the line of duty, kills outlaw Joe Land and adopts his young son, Tim. They come upon a former silver boomtown, reputed to be haunted, whose only inhabitant is Hiram McDuff, a friend of Bill's. Ranch owner Joan Stanley hires Bill and Tim. Her father has been killed by the gang of Wolf Larson. By mistake, McDuff hires the Larson gang on as ranch hands for Joan. They plan to steal the stock while Bill is away. Tim overhears the plot and informs Bill. Bill and Tim use ghost makeup, skeleton sheets (even outfitting their horses with skeleton-looking blankets) and tricks to rout the superstitious gang members...