Thats the bathroom door.
I asked the sister about it, and it turns out she was talking to herself in the room next door to the bathroom.
I have so many questions.

basically I will not get out of bed at night in case the burglars, who are of course not real here me. this includes trips to the toilet. And this makes quite a bother when you need to go. Because the burglars are watching me and will kill me because I am not in my bedroom.