To be honest, I don't really know what to say about this film. It is creepy more for its seedy underbelly of a woman caught living on society's fringe (which Friedkin does an excellent job of depicting), than it is for it's final horrific half hour, which, while making me squirm (pulling your own tooth out with a pair of pliers was truly an impact moment), didn't have the emotional impact of what had gone on before.
To me, the story is more about a lonely loner type woman who seems somehow a step out of sorts with those around her. She plays kissy face with a fellow barmaid (obviously a dyke), does coke with her and her aquaintance, yet doesn't want to accompany her to a party. She is obviously bi, and yet the hints are there that it's more a statement about lonliness and trying to connect than any commitment to any kind of sexuality, other than her innate need to be dominated. Her lonliness is amplified and the signals are subtle; she seems tethered to an abusive relationship with a con who say he loves her, but it's obvious that he only loves that he can control her. You begin to wonder about her, if all the phone calls at the beginning of the film, where there is no-one there when she answers, are legit.
When the story comes out about her child's dissapearance you begin to see the cracks in her facade and that her little tough girl routine is, as the song cleverly plays in the backround, just a masquerade.
This makes the absurdity that follows at least somewhat plausable, and it is a revelation that she is just as unhinged in her own way as the lunatic who believes that his body is infested with government planted bugs.
There are times when it is obvious that this screenplay was developed out of a play, but for the most part it remains just quirky enough to hold your interest; at least until the final payoff, which is a major letdown which, I suppose, is where madness eventually leads to, but it still comes off as a contrived bit of theatre.