When it starts off, you think you know where it's going, but then...
it takes another turn and keeps you guessing. Clever ending ;)
The writer wrote some other good movies: The Entity, The Two Worlds of Jennie Logan, Trapped 1973, Audrey Rose, and one that I haven't seen yet - but is on Amazon - the Penthouse.
Spoiler: The production design of R Bailey's apartment was fantastic. From the first scene in this apartment until the end, the movie keeps up. Really interesting details and set up.