Again, I don't understand why anyone would answer the door if the hour is late and you are not expecting company. Anyone with legitimate business can/should call first. There's just no reason I can think of to open your door to a stranger at night.
Well, it just might be a person truly in need, or maybe there are flames shooting up from my roof.
I would probably open an upstairs window and holler down to them if we were in bed already.