Horror movies that are like plays?

I'm watching some of Existenz this morning. I hope I don't sit here long enough to watch the whole thing, it would be better to go out and do something in the physical world. But, just to mention this... I have always been struck by how much Existenz (and some other Cronenberg films) feels/feel like a play. Not completely, but often, and certainly much more than many other movies.

The Ashley Judd/Michael Shannon movie Bug reminds me of a play at times, too.

I know I have thought this before, about other horror movies, but nothing is coming to mind right now. Wait, maybe Misery, at times... there are other movies though. Anyone else have anything that comes to mind?