The true tragedy of this film doesn't lie within the backstories of its' characters -- it's that it had so much potential to be a much better film.
It had - in my opinion - everything going for it: an interesting plot, compelling characters, an eerie and atmospheric setting... oh, and Imelda Staunton.
And somehow it managed to toss all those things aside in the last ~40 minutes of the film in lieu of a not particularly clever twist that had very little, if any, build-up.