Thinking that you were going into a shop, you open the door at the top of the stairs and find yourself by mistake in a private house. Someone is putting on a hat in front of the hallway mirror, a tall and thin person of monstrous proportions, with a face so long that they look like a rubber human who would have been stretched.
You immediately close back the door while muttering confused excuses and walk back down the stairs with the feeling that you saw something that you were not supposed to witness.
Many of those people may exist behind common doors and façades. They may well be human. Or not. You know what to do if you ever want to find out.