Possible plot hole
One thing in this movie looks like a plot hole to me. When the young doctor is first given a tour in the asylum by Ben Kingsley, the Kate Beckinsale character is presented to him as one of the patients. Why was Kate Beckinsale not pretending to be a stuff member, given that she was one of the saner ones in the asylum? It would have made sense for Ben Kingsley to present Kate Beckinsale as the head nurse or something.
Of course, the movie could not go that way because then the young doctor would have realized immediately that something is amiss. But Kingsley did not know that the doctor had met Beckinsale before, even Beckinsale herself did not remember that. So there was no logical reason for them to have Beckinsale play a patient. It's not a big deal, of course. Just something I noticed.