Yes it's true there really isn't any strange and deadly occurrence in the film--though you could argue there are several. You could also say that not much really happens in the film--despite these, I feel, truths about this still obscure movie, it's worth watching.
I saw it as an adult in a poor copy that still couldn't ruin the film. Much credit to the director and to a set up that feels like the Manson family is about to attack at any moment--but don't expect that kind of pay off as there is more dread than actual action in the film. Shows what a good cast and director can do--at least back then. Robert Stack is especially good. And the late appearance of Deliverance crazy McKinney makes the ending much more satisfying than it should be. One of the great creepo character actors at the top of his form.
Today this would be made for LIFETIME in a lifeless way. And if they did, they would cut the "headless" scene that is the horror highlight of a movie that isn't really a horror film. I suppose if you saw this as a kid you'd say it was the headless movie though that is one isolated scene with little or nothing to do with the rest of the film.
No the film is not in the same league and the great scary 70's TV movies, but it's way above par for what passes as TV thrillers currently.
Sandor Stern as one of the writers is a plus as well. This just shows what talent and craft can do with a very limited story concept.