Howling:Rooms

Have you ever noticed that in "The Eleventh Hour" when The Doctor asks Amy how many rooms are on that floor she said 5, but there where only 4 doors apart from the one where the prisoner zero was. But if you look closer you can see that there where 4 doors, 2 staircases and the room where the prisoner was.

I don't know why but this all lead me to the dark lord but that is WAY to easy i really hope that Moffat don't make the whole thing an obvious end.

And here are a lot of theories about a new TARDIS, that could work too.

The fact is that or that was a mistake or the staircase lead to something important.