The New Old House

Every Tuesday during Halloween month I'll post a Halloween related prompt. Here's the first one. See if you can get a creepy, spooky story out of this.

You are visiting an old mansion. It is three stories high and has 13 rooms. You have to climb 13 stairs to get to the second floor and 13 more to get to the third. Sometimes you're sure you see a face looking out of a third floor window. Your first night staying there you here a squeaking out on the stairs near your room. You are afraid to go out there (maybe you've heard stories about this place). The squeaking does not stop. Eventually you can't stand it anymore and creep out of your room to look. There is a mouse sitting on one of the steps. What happens next?