From a Redditor:
I, with absolute certainty, experienced a malicious haunting.
I was living in England as a missionary (Ex-Mormon). We had just moved flats because the sister missionary pair had been taken out of the town due to lots of harassment while they walked around. Their flat was way nicer than ours, so we got the go ahead to move in.
The sister missionaries had all had a terrible time for years in this town. Sickness, depression, physically fighting one another—you name it. While I was there, one sister broke her foot, another had become incredibly depressed, and another had developed a heart condition.
We move in after they leave and immediately things start to get weird. My companion and I become mean and bitter to one another. We were fighting constantly over the most ridiculous things. I couldn't sleep (which is never usally a problem as a missionary because by the end of the day you're exhausted) and I was losing track of time. At one point, my companion and I realized during our study time that we'd both just been staring at the wall, completely zoned out, and had no concept of how long we'd been doing it.
The worst part, though, was that I could not shake this feeling that I was being watched. It always felt like if I could just turn around quick enough I would see someone standing right behind me.
One day we get home and I stay downstairs while my companion goes upstairs. Technically, you're always supposed to stay within sight of one another, but when you're in your own flat most tend to drop that rule. Well, eventually I hear him messing around in the kitchen. There's a window in the living room that you can see into the kitchen but it's fogged glass, so it's really just shapes and outlines.
I looked through that window and I saw the outline of my companion moving around in the kitchen.
Not even a minute later and I look up to the sound of my companion come bounding down the stairs. I asked him when he'd gone back upstairs, and he replied that he'd never come downstairs since we'd been home.
My blood ran cold and I immediately had this all consuming feeling that I was being watched. I panicked and told my companion that we had to leave. Every fiber of my being told me that something awful was about to happen to us. That whatever was there hated us, and would hurt us the moment it found a way to.
A few seconds later, our phone rings. It's our zone leaders calling to tell us that they'd had a random feeling to call us and tell us that they wanted us to pray over our flat. Neither I nor my companion had called or told them anything. We did, and immediately it all felt better.
After that day nothing ever happened again. I'm no longer religious, but I can't explain or deny what I felt and experienced.