Strange "Illusion"

 More than one strange item today. After my wife and I closed up the store we headed home. We both drive and I got home a few minutes before my wife. I unlocked the rear, western, kitchen door and was greeted by my dogs. I walked through the kitchen into the short downstairs hallway where the backstairs go up to the second floor. As I stood in the hall, taking off my coat and hanging  it up I looked into the Dining room to the door that leads into the parlour. My house, like most old houses, has large interior doors that are just short of one half inch off the floor. I'm  sure that if you have ever seen doors that do not hug the floor or carpet you  realise that anything beyond that door moving close to the door is evident as moving shadows on the other side of the door, As I watched, I saw definite movement in shadows under that door. This gives you a real start. Moving forward quickly, I opened the door. Much to my relief nothing was there. But what made the movement and shadows I saw under the door?  It was possibily an illusion; but it can still give you a start and what created the illusion to begin with.                     

I say things are quiet and then things happen. I had to open the wife's store today because she needed to go to a big town and pick up needed merchandise. The store opens at 11:00 am so I was there at 10:30 am. I unlocked the door and went in; before I could even turn on the lights I heard a very small child run flatfooted on our hardwood floors. The child ran the entire length of the store. I turned on the lights and there was noone in the store but me. It sounded like a child because young children tend to run flat footed and make a slapping noise as they go. Someone suggest that maybe it was a mouse. I suppose it could have been if the mouse weighed 20 or thirty pounds, wore hard soled shoes and ran flatfooted. Somehow I doubt it.