The Beast from Haunted Cave is some sort of wannabe heist gangster flick with a sci fi horror twist. Of course, given that this is Corman cannon fodder, you get to sit back and take the horror sci fi for what it is sure to be the moment you press play: tiny insert shots, and a loooooong wait to finally see the monster in the last two minutes. Corman was king of making you wait for the very ass end of the film for you to get any sort of payoff. I wonder if he did this to make people walk out of the theater saying, "that movie wasn't that bad," the ending of it still fresh in their minds.
What is the plot besides the fact it features a very indiscernible monster that makes occasional guest appearances? Some bullshit about some gold bars that are in the mountains. A couple of these criminals set off some explosives in the hills and awaken the Beast, which is a giant spider by the way, and it kills one of them. The other gets away but now is terrified of what he saw, and what no one believes him about. All becomes clear when they witness the Beast kill someone else, but they've still gotta get their gold so now it's one last confrontation, man vs. Beast....
The monster in this movie is awful. Here is the poster of the movie:
Awesome! It's some sort of tentacle monster with huge fangs and there's webs everywhere!
Then the monster we got in the movie:
It's uhhhh, some dude covered with hay and string draped all over him? It's Cousin Itt from Addams Family? It's a close up of something my cat threw up? This could literally be anything.
So as you can see, this movie doesn't exactly "deliver". It's genuine Corman, at least, and we knew what we were getting in for, but this one has to be one of his worst. At least others distract you with how silly the monster looks, or with a somewhat interesting side plot. The plot in this one is so flat though, and poorly acted, that it pretty much fails in every conceivable way.
I will give it this: if you went into it not knowing what the title was, and not knowing anything about Corman, there is a small chance you might get caught up in the plot and wonder wtf is with the spider thing. Because like so many of the movies of this era, it doesn't explain jack shit, which is great if you were super high and drunk. It could be entertaining like that. But the plot moves so slowly you'd eventually just decide to watch Robocop II instead.