Who goes there?

A few nights ago I was sitting on the computer reading through posts on Cafemom. The only people home with me at the time were sound asleep here in the living room. 

I suddenly heard a door open upstairs and someone walk slowly down the hallway and then down the stairs. I thought nothing of it at the time because I am so used to the sound, but then it hit me....no one was up there!

I literally heard them come all the way down the stairs and actually got up to check expecting to see someone standing on the bottom step. Nothing.