It’s Alive – 1968 – United States
The story of Tommy Kirk (star of It’s Alive) is way more interesting than this movie. He acted for Disney until he was outed as gay and got fired. He was hooked on drugs for a while, and to pay the bills, he made a lot of crappy movies like this one.
A couple of New York yuppies are on a road trip in the Ozarks when their car runs out of gas. They coast into a rundown tourist attraction operated by an animal tamer named Greely. Greely seems friendly enough, but he is actually a total psycho who abuses his housekeeper and keeps a mutant fish-man in a cave on his property. He traps the yuppie couple in the cave along with a paleontologist who just happened to stop by. The prisoners escape and blow the cave up with dynamite, sealing the creature away forever. Maybe. We can never be sure since the ending title card reads, “The End?”.