That old, familar, creepy feeling

Have you ever gotten the feeling that there is something in your house that shouldn't be? That's been happening lately. My room mate and I have been seeing shadows lately. And my cat Mr. Vinny has been acting weird. He's been running around the house, ears pinned back, like he's running from something, and then stop short like he's trying not to run into something. I have seen other cats do this, but only in houses that supposedly have spirits in them. Granted, I grew up in a house that had a spirit in it, so the feeling is nothing new, but this spirit is new. We have lived in this apartment for almost a year, and it's only been the usual, family spirit. This one is definitely new, and lurks all around the house. It almost makes me want to find out why it's there and where it came from, almost. If it keeps creeping us out and doesn't move on soon, I'll find a way to gently push it out. And if it doesn't want to go quietly, well, let's just say that the lease will be up and the end of February.