Local residents believe that the disappearance of a cowboy's cattle is due to a monster that lives within a mountain surrounded by a swamp.
I believe that this is the first real take on Willis O'Brien's Gwangi concept combining cowboys and dinosaurs. It's not really very successful; the movie is three-quarters through before we ever get a glimpse of the beast, and most of the preceeding sixty minutes is fairly dull by monster movie or western standards. Things do pick up around the forty minute mark; there is a scene in a graveyard that actually generates a fair amount of tension, and a stampede sequence that is probably the highlight of the movie. The monster itself is generated via stop-motion, but using a series of static models versus a poseable model; this gives the dinosaur a range of expressions that it wouldn't have gotten conventionally, but it's far jerkier and less effective than more standard stop-motion, and you see entirely too much of the dinosaur sticking his tongue out and waving it around. It must have been a difficult and expensive process, too; that's probably the main reason the movie takes so long to get to its few dinosaur scenes. Still, the second half is much better than the first half.