This film isn't a big budget film which may put off some viewers from the outset. It is very good if you're into this kind of thing though. The horror is not too explicit, but is more suggestive, and this actually makes the film genuinely creepy in parts. The performances are a little amateurish by the lower cast members, but Peter Cushing is in commanding- if all too brief - form and John Carradine gives a good perf. Brooke Adams also registers well in her acting debut. The plot is daft yet manages to convince, mainly because there is a really neat exposition scene in which Cushing explains what is going on. He's such a persuasive actor that even though the whole idea is so preposterous, when he says it you kind of feel compeeled to believe him. I rate this flick and would hope that anyone reading this at the moment would go out of their way to try to see it. It's worth the time and has a weirdly effective way of sticking in your mind for a long time afterwards.