Thoughts whilst falling Asleep last Night

As I fell to sleep last night, a thought disturbed me. If I reached out with my right hand -and sat up in bed a little- I could touch the door of my bedsit. For no reason at all this thought bothered me. Through half-opened eyes, I regarded the door with suspicion, and as I lay there, within touching distance of the door, I then began to think: what would I do if there was a knocking on that door?
And in the darkness of my room, half asleep, this was the most terrifying thought of all.