Late Grandmother's Mansion

NB:
This is a kind of creepypasta that I have heard referred to as a Creepy Thinker. Hints are dropped here and there throughout the story, that give you the reason as to why it is creepy. Some will understand it right away while others have to struggle for it. If you get it, please post your solution on the story talk page (unless it's already there).

______________________________________________________________________________________________

I unlocked the heavy wooden door of my late grandmother's mansion and pushed it open, rushing into the hall. I went straight to the cupboard at the far end, keeping my eyes fixed directly on it, meanwhile muttering irritatedly under my breath at having to venture into the building alone.

Truth be told it scared me shitless to be even near the mansion. I'd much sooner volunteer as a test subject for new medicines than freely enter the mansion. That's one reason I'd been there less than 10 times in all; another reason is that my grandparents had never been much the company of others, not even family. My mom says it used to be different, but she won't say anything else about it.

It didn't really matter either. All I cared about was that I always had this really creepy feeling of not being alone in there, even though my grandparents lived alone, and after her husband passed away a few years back, my grandmother had been living alone.

However, today – when my mom and I were on our way home from her last parent's funeral - she had insisted that we make a stop at the old mansion, and as had a limp, that I ventured into the terrifying depths to get her mother's old cookbook, just because she didn't feel like waiting a few days until she and her sister would go through their parents' belongings. But even though I'm quite a coward, I was way too embarrassed to admit, even to her, that I, a grown-up man with wife and kids of his own, was too afraid to fetch a book from an empty building, so I agreed without much resistance.

When I reached the cupboard I put the key to the front doors on top of it and pulled the uppermost drawer out. There were only a few books in there, all of the old and dusty, and I quickly located the cookbook. With it in hand I closed the cupboard drawer and marched back to the open door. I pulled it closed behind me and almost ran down the short path to my car and my waiting mom. I got in and handed the book to my mother, suppressing a sigh of relief.

“I didn't see you locking the door, sweetie.” my mother said, and – heart sinking – I realised I had left the key on the cupboard inside. I muttered something about my bad memory as I got out of the car again, feeling horribly foolish for making such a mistake. As I went up to the front door once more my muttering turned into curses, this time out loud, but not loud enough for my mom to hear.

I breathed deeply and exhaled once before pushing the door open again, and for the second time I rushed to the cupboard. I got the key and turned back to face the door, and as it slowly and soundlessly swung shut under its own weight, I felt the blood in my veins freeze in true horror.