Starring the Three Mesquiteers, some say Riders of the Whistling Skull is the best B-movie Western ever made. The plot involves a missing archaeologist, murders, an ancient city that may or may not exist, an ancient cult that may or may not be murderous, a curse, lots of plot twists, and three cowboys. It has been compared to Scooby Doo.
This movie is in the Public Domain and thus legal.