The Chimney
This happened about 7 years ago at my high school graduation party. Rather than rent a venue, my father managed to rent a historical house for the day for free (since he used to volunteer there). It had a nice yard where the party was held, and the interior was furnished to look like it did in the late 1700s/early 1800s (the same time period when the semi-famous historical figure who owned the house would have lived there).
I had been inside this house many times and honestly loved it. It felt like going back in time. Anyway, I was showing my high school friends & some cousins around the house (we gave people impromptu tours as a party activity).
I was wrapping up the tour on the second floor when I suddenly noticed an open door in one of the bedrooms. It caught my eye because it was always locked, so I figured it was a maintenance closet or something. Not only was it open now though, but the light was on, suggesting someone was in there.
I instantly felt uneasy, since my father had stumbled across a homeless man in one of the town's historical homes about a year earlier. They had broken into the house to escape a winter storm and were hiding in one of the bathrooms.
What if someone had broken into this house before we arrived and were trying to hide in the maintenance closet? I considered telling my father but decided to investigate instead (since there were about 7 of us, making me feel a little safer).
Turns out the door wasn't a maintenance closet at all, but instead led to a long, narrow hallway that ran along the length of the house, like a secret passage that connected the two bedrooms.
My friends and cousins followed me inside. We made it about halfway through when I noticed another door to my left. This was weird, because from my understanding of the house's floorplan, there was no way this door could lead anywhere (unless it was a narrow closet or something). I decided to open it anyway, just to make sure no one was hiding in there.
The door opened easily to reveal the darkest room I had ever seen. It was so dark that you couldn't even see an inch in front of you. It was also freezing.
No one wanted to investigate further (saying it was too creepy), but my cousin C and I were curious, so we took a step forward to look inside. I still had one hand on the doorknob though, because I was weary of a potential intruder and wanted to be ready to quickly close the door if need be.
But as soon as C and I stepped forward, I felt someone tug on the doorknob. And not just a light tug -- I mean they pulled it with such force that the doorknob on my end was yanked from my hand. The door slammed shut with such a deafening bang that we all screamed.
I immediately went to open it again but the doorknob wouldn't even move this time. It still wasn't locked, but to my horror, I realized that it felt like someone was holding onto the doorknob on the other side.
Terrified, I motioned to C to try to turn it, but he couldn't either. Finally, he turned to me and whispered "Someone's in there."
At this point I knew we weren't alone, so I just screamed at everyone to run.
We made it outside where my father was serving drinks. I began to tell him about the person in the hidden closet. I was only at the part of my story where we notice the open door when my father interrupted me and said "That door shouldn't be open. I hope you didn't go in there -- it's not safe."
I told him we went in but when we opened the closet door on the left, someone slammed it shut. I remember my father's eyes widening as I said this. He looked extremely troubled.
I asked him if he thought it was a homeless person like before, but he said it was impossible. When I asked why, he said "That door doesn't lead to a room or a closet -- it opens into the old chimney. If you had stepped inside, you would have fallen three stories and ended up in the basement. That's why we always keep that hallway locked...I don't know who could have gone in there. I have the only key."
At that point, I just remember C and I looking at each other in utter confusion. On the one hand, it made sense now why the room was so dark -- there was no floor, so the light from the hallway had nothing to illuminate when we looked inside. It also explained why it was so cold. But if there was no floor, how did someone slam and hold the door shut?
Disturbingly, my father also said that the chimney was sealed off decades ago when the house was relocated to the center of town, with the second floor "door" acting as the only way in or out (apparently the law required that there be access to the chimney for future home inspections, so they couldn't seal it off completely).
In other words, they literally wouldn't have been able to retrieve our bodies unless someone rappelled three flights down the narrow chimney to get us. Even if we somehow survived the fall, we probably would have succumbed to our injuries before anyone had a chance to get down there.
I still stand by the fact that I felt someone pull that door shut. C also backs me up and says that he knew he felt someone holding onto the doorknob. We often joke that it was a ghost who wanted to prevent us from being stupid and falling to our deaths. But I still have no logical explanation for it.
TL;DR: A ghost saved my cousin and I from falling three flights down a historic chimney.
Edit: a few typos & length