strange activity early this year

     Strange activities are early this year. Today as I was answering E mail from the computer in the Library, I distinctly heard heavy footsteps go though the Diningroom. My wife was not at home, my dog was lying in the floor in the Library but facing the doorway into the Diningroom. When the steps were heard, my dog began growling; obviously he heard them too, and for whatever reason, but did not assiociate them with my wife. Which, of course, they were not. Moments later a door was shut hard, almost slammed, and the footsteps, lighter this time, again crossed the diningroom toward the parlour. This time the dog growled and moved away from the doorway toward the den. I left the computer and checked the Diningroom , Parlour and Kitchen. I found no one and nothing amiss. My wifes car was not in the driveway, so she wasn't home to make the sounds.