You wake up to a strange scratching at your window. You sit up, and look blankly at your wall, which is in perfect order. You lean slightly to one side and tilt your head to hear the sound better. You realize it's just the tree's leaves scratching your window; after all it's a windy night.
You lay back down, and after about five minutes a tapping noise awakens you once more. You repeat what you just did, you lean over and tilt your head; it's definitely a tapping. For a minute you become paranoid, but you realize that after all it is winter, so a majority of the foliage has died and fallen off; it's just a bare branch hitting your window.
You're just about to lay back down, when you hear a hissing. Of course, it's just the wind blowing through the dead leaves, and the "hissing" is just the leaves rustling among one another.
You laugh to yourself, and lay back down.
But then, you jump straight out of bed in a cold sweat.
You don't have a tree outside your window.