The monster in question is a frog-type monster that lives in a lake in Wisconsin. A man relates the story of his youth with his father and how he came to know the beats existed in the first place.
Indians used to worship the monster as a God and it is believed that the monster also protects a large stash of gold. Three men attempt to steal the gold and are killed in horrible fashion such as being torn apart or having their face smashed into a tree trunk.
The ending of the film leaves it open for a sequel. Now, I happen to like this film, yet I really can't define why. It is Rebane's homage to "Creature From The Black Lagoon" and it is super low budget with a no name cast, but something always makes me like this film. It could be that I am a real fan of regional horror films.
I hope this makes it to DVD or Blu-ray someday besides the silly Troma release it got a while back. If you are lucky enough to run across this title I suggest you check it out.