Heavy walking and stamping

    Last night was one for the book. The day before Thanksgiving and everything was basically ready for the big day. Evening found us relaxing in our usual manner. My wife was talking with friends on the computer and I was half watching TV and doing some sketching. The dogs were in the Library with my wife, half asleep, between the computer and the doorway to the Den where I was located. My wife got up from the computer and walked to the Den doorway. She said "will you turn off the sound?" This seemed strange to me as I didn't think the TV was loud enough to even be much heard in the Library, but I turned down the sound. "Whats up?" I inquired. "Listen" she replied. Sure enough it sounded like footsteps, or rather hard soled bootsteps on a wooden floor. "Wheres that coming from?" I asked. "Sounds like upstairs", she informed. No bare wooden floors on the second story of our house, all are wall to wall soft carpet. I said I'd investigate and headed for the stairs. My wife and dogs remained downstairs. The sound of steps walking and stopping and stamping continued. As I went upstairs the sounds became clearer, louder. Unlike other times when the walking sounds lasted from a few seconds to perhaps as long as 30 seconds, these were continuing. I determined they were coming from the attic. Brave soul that I am, I armed myself with a 44 mag revolver and a big flashlight. The steps and stamping continued right up to the moment I opened the attic door. Then everything was silent. Cautiously I  made my way up the old narrow attic stairs. At the turn in the stairs, on the landing, I stopped and pointed the light around, but still being below floor level, it didn't help much, so I went on up.  There is one 40 watt bulb in the attic and it has to be screwed in to light (the string broke some time ago.) Carefully making my way over to the bulb I screwed in the light. The light is dim in that big attic and mostly just cast shadows. The light does not penetrate the larger section of the attic which is walled off except for a doorway. I figured that if someone was up there I had better search the lit part first. Like most attics, ours is filled with stuff too good to throw away but not good enough for much use. A 12 foot Christmas tree for example and an ancient kiddie car I had as a kid. I have pathways through the attic and I took each one until I was satisfied there was no one in that part. There are only two ways into the attic. Through the door at the foot of the stairs which we keep locked with a slide bolt (thats because my wife believed bats were pushing through to get down into the house) and the hatch to the roof which is also locked from the inside with two slide bolts (when we first moved here the hatch blew off a couple of times during bad storms, so now its locked). I checked the hatch and it was still solidly locked. That only left the large front half of the attic. Frankly, this time, I was feeling pretty darn sure we had an intruder some way. Moving into the front section I played the flashlight around all walls and ceiling, the flashlight is one of those new 80 light digitals and it was like a spot light, it lit the attic room. But I have items stored in there in rows up almost to the ceiling, so I needed to walk those isles until I covered the attic area. I found absolutely nothing. Returning and going downstairs my wife and the older grey dog were at the foot of the stairs, she had a moveable gate across the stairs because she said the dog wanted to come up where I was and she was afraid I might shoot him. I was tense, but I really don't think I was that tense. I asked her if she saw or heard anything after I went up to the attic. She said she heard me walking around but that was all. Laugh if you wish, but something like that can really get to you. What in blazes was it? A big mystery in the strange old house.