Creepy, underrated movie!

I haven't seen it for years, but I remember I enjoyed it.

It was creepy. I watched it in the dark last night (second time seeing it) and when the lights go out in the elevator my TV goes into a kind of "off mode" so it's not even dark grey, it's like it's switched off. It was quite eerie knowing something is gonna happen again and then those scary violent sounds start. At one sage stage you see this horrible creepy grey head appear for an instant from a wall behind someone when the light flashes.