Knocking

 Scary stories from around the internet translated into English.
 ---------------------------------------------------------------------------------------------------

I was on a business trip with a coworker. We stayed at the same hotel, so we stayed up talking for a while. He kept trying to freak me out by telling me that the place was haunted and that something was going to come for me in the night. Admittedly, I got kind of scared and when I went to bed I made sure to cover myself as much as possible. You know how it is.
Just as I expected, I heard someone knocking at my door in the middle of the night. I thought it might be a hotel employee, so I called out to see who it was. Nobody answered, though. I was scared even looking at the door, and the knocking continued all night long. As soon as the sun started to come up, the knocking stopped. I got dressed and hurried out of the room. I checked out without even eating breakfast because I didn’t want to be anywhere near the place.
After the business trip ended and I went back home, I told my coworker about the knocking. He smugly said that he knew it would happen because a while back, there had been a fire at the hotel. Most people made it out, but there were a few that had been stuck inside. Those people ended up being stuck in their rooms and died slowly from burns and smoke inhalation. It’s their spirits that appear at the hotel now.
Damn. Hearing that made me glad that I didn’t open the door. I wonder what would have happened if I had?

What makes this story creepy?