This looks awesome.
Mental asylums are a great place to scare the shit out of you, especially by the look of this one.
I don't think Leo being No. 67 is the main twist of the film. That would be too hokey, something reserved for a contrived slasher filck - not a Scorsese picture.
Could be the plot revolves around no. 67, and is a character study into Leo's descent into insanity?