It happened eight years ago, but I remember it like yesterday.

The wedding had been a busy one. Between helping out at the reception venue, getting the groom to the church on time, and then dancing for hours with one of my best friends (who happened to be in the wedding party as well), I was beat. Many of the wedding party were staying at the bride’s family’s large mountain lodge— an ancient place adorned with trophy animal heads, old family portraits, and unknown history. I had been sleeping on the floor in a guest room, so I was more than excited when the pastor who performed the wedding decided to leave unexpectedly early. He and his family seemed in a hurry for reasons they didn’t share, but it meant they left the second floor bedroom vacant.

Thrilled to have my own room, I pulled the door shut and crawled into bed, the wood-paneled room lit by the incandescent glow of the bedside lamp. White curtains framed a moonlit window, and a child’s rocking chair sat in the corner next to a fireplace. The only sound was the occasional exhale of the air conditioner. I turned off the lamp, and in the pale light from the waning moon, it looked like the curtains were billowing up. The chair appeared to rock slowly back and forth— perhaps a trick of the clouds passing over the moon outside or perhaps something else.

That’s when I heard it: three gentle knocks on the thick wooden door.

Thinking it was one of my friends in the other rooms, I turned on the lamp, and walked to the door. I opened it slowly only to see… nothing. There was no one there. Perhaps someone had gotten my door confused with someone else’s and walked away; after all, we had been at a wedding reception, and many of the guests had significantly more to drink than I did. I went back to bed.

Again, in the silver moonlight, the curtains seemed to billow, and the chair seemed to rock, and then I heard it a second time: three pronounced knocks on the thick wooden door.

Moving more quickly this time, I jumped from the bed and ran to the door just a few feet away. When I opened the door, however, I again saw no one. Tired and frustrated, I looked around the hallway. I wondered if my friend in the wedding party was playing a prank on me, but there was no way she could get away from my door so quickly and silently. There were stairs going up and down from my room in either direction— not something you could easily walk on quietly, and I hadn’t heard any footsteps. There were no corners to hide around. What was going on? Still, I needed to get some sleep, so I got back into bed.

There was no mistaking it this time. The chair was rocking gently back and forth as the curtains billowed and the waning moonlight filled the room. And again, at the thick wooden door, I heard the sound a third and final time: three loud knocks— so loud the door shook in its frame. I sprang out of bed and threw open the door, only to be greeted once and again by an empty hallway.

And so I went downstairs and slept on the couch because, while I still don’t believe in ghosts, why take chances? I didn’t know the history of the house, and I chose never to ask the bride, but to this day, I wonder about the history of that rocking chair and the former occupants of that room and how they met their end.

Every good ghost story has certain tropes: an untimely death, a creepy location, sinister signs of the soul’s lingering presence. In our folklore, ghosts are the tortured spirits who linger on earth for myriad reasons, but all of them tie back to something that went wrong in their lives. There’s always something tethering ghosts to this world, whether they’re haunting houses, people, or the locations of their physical remains. A good ghost story always leaves some mystery to it, priming our minds to experience sinister sounds and sensations without ever getting too specific. If we’ve been prepared enough by a good ghost story, a cool breeze flowing through a room might be enough to terrify us.

I like to think of ghosts the way I think of dreams. Even though we’re asleep, our brains still experience stimuli, and our sleeping minds try to make sense of these sensations by building stories around them. A ghost experience works along the same lines. Was the chair really rocking? Probably not, but my tired brain certainly built that narrative. Were the curtains billowing because of an unseen specter? More likely, it was an unseen air conditioner vent or an improperly latched window allowing a breeze, but good luck convincing my brain that. Were the knocks on my door really some otherworldly entity trying to get my attention? A more realistic explanation would be pressure changes caused by other doors in the house opening and closing, but after the long day I had, there was no way I could reach that conclusion.

Our brains are incredible storytelling machines, and put in the right context (like an eerie room in an old secluded mountain house), they can create some bone-chilling scenarios.

And that’s why ghosts are scary.