Corrected entry: In the last scene, when Scott and Angie are up in the attic, someone opens a trapdoor above them. When Scott uses his camera to see what's there, there is a girl-like creature who slams at the camera. Later, however, there is a man ("the man from Boston?") roaming around the room. There was never a mention of a girl living in the attic. And it couldn't have been Briana because the door was locked and there was no other way of entry.
Corrected entry: There appears to be some ambiguity as far as who the afflicted person in the attic was. The assumption is that this individual may have been the "man from Boston", and if so, it presents the problem of a missing character in the film. In the movie, there is mention of a sick old man who resides with the foreign (non-English speaking) couple, however, no attempt is made to rescue this man, nor does he appear in the movie.