Actually, after thinking about this episode some more, I think it was a big cop-out by the writers...
The idea of a place between Life and Death is certainly not a new idea. There was even a film called 'Flatliners' in which medical students begin to explore the realm of near death experiences, hoping for insights. However, after setting this place up that brain-dead people go to before the plug is pulled on them, half-way through the writers back-track on the idea, and tell us that it is only a one-off circumstance. It only happened because Audrey Pauley made it happen, and because those people had really been murdered by the Doctor.
This never usually happens in an X-File story, usually the plot is much more hazy, leaving more than one explanation possible. IMHO they realised that this was a very contentious issue and so escaped any criticism by deliberately making that point very clear.
What they didn't explain was why the Doctor was killing his patients? They mentioned 'Doctor Death', but in the very small number of cases where Doctors have killed their patients, they did still actually have a motive -- some misguided 'Euthanasia' or 'for personal financial gain' in being a will benefactor. So, what was his?
At one point they almost were heading towards an 'organ transplant donor' motive, in fact, Doggett seems to have a really big problem with organ transplants, without any explanation given.
Maybe this episode had a major rewrite, that can happen, and they originally meant that to be the story, but it was such a contentious issue that there was a block put on it. I know that in the UK, such a story would be unlikely to be shown, after the events in the Alder Hey children's hospital.
If there was ever meant to be a reason for Doggett's aversion to transplant surgery, I doubt that we will ever find out now.
Also, what happened to the nurse the Doctor murdered? Why didn't she get transported to the house as well. If she had, she could have told Monica the whole story about half way through the episode, and they could have solved the riddle much more quickly.
Sorry, but I just didn't like this episode at all!