This is something that happened to me fairly recently.

Each night when I go to bed, I always close the door to my bedroom. Over the last few days, however, I would settle down into bed and just be dropping off to sleep when I would hear a faint knocking.

Knock, knock, knock.

Three slow, faint knocks on my door, just like that. I asked my flatmates about it (thinking it could have been one of them messing with me for a bit of fun) and they denied doing anything of the sort.

So last night, I decided to try something different. Around the time I would normally go to sleep, I stood behind the door and waited for the three knocks. When the time arrived, I heard the knocks again, right on cue.

Knock, knock, knock.

As soon as I heard them, I grabbed the door handle and flung open the door, hoping to see who was there.

Nothing but an empty corridor.

I stood there with the door open for a few moments, feeling rather perplexed, then shrugged and went back to bed. Just as I was dropping off to sleep, however, I heard the knocks again.

And this time, they were coming from the bedside table behind me.

Knock, knock, knock.