If you want to make a claustrophobic movie that hinges on the interaction of just a few characters, those characters have to be able to carry the entire narrative. This movie hinges on you feeling the panic of a person being locked in a small moving room with an ominous voice in the background talking to her. However, the voice is not scary and the person locked in the room is not convincing and the overarching narrative is never made quite clear, nor are the rules surrounding the antagonistic presence consistent enough so that you could build tension off of it. The result is a movie that feels cheap and underwritten, where this should probably have gone through a few more rounds of edits before it got committed to celluloid or video.