Possible Ghost

I had just gone to bed one night about a year ago, sometime between 2 and 4 in the morning. Both of my parents were gone, and it was just me and my sister in the house. Her room is upstairs right next to the top of the steps, and my room is in the basement, right next to the bottom of the steps. I also have a cat (which is my only pet), and she was sleeping on my bed at the time. I had my door cracked open slightly so the cat could get out if she wanted. Suddenly, the doorway lit up like someone turned on a light, and I heard footsteps going from my sisters room, across the house to the garage, which is at the other side of the house. Once the footsteps got about halfway across the house, the light turned off and the footsteps stopped. I didn't think anything of it, because i figured it was my sister getting up to do something.

About 5 minutes later, I never heard the footsteps come back, so I got up to see what my sister was doing. When I looked in her room, she was in her bed asleep. I woke her up to ask what was going on, and she said that she had been asleep the whole night (I would also like to add that she has no history of sleep walking, and that i never heard the footsteps come back to her room). That really freaked me out, so I grabbed a knife from the kitchen and searched every inch of the entire house. I did not find anybody, and nothing was out of place or missing.

I decided to watch TV in the living room until my sister went to work the next day, so I could keep watch. After she went to work the next day, I was sitting in the living room still watching TV, and I suddenly heard an extremely loud crash coming from the garage, which is on the other side of the wall to the living room. It sounded like someone took everything in the garage and dropped it all on the floor at once. That really freaked me out, so it took me a few minutes to work up the guts to go look. When i finally did, there was nothing out of place or on the floor or anything.

You may be thinking that there was a burglar or something in the house, but I know it wasn't because a.) a burglar would not have turned on a light and walked noisily through the house, and b.) When I heard the crashing noise, I did not hear any other noises. If it was a person stealing something, I would have heard them picking the items back up, and I would have heard them opening the door in the garage to run away. And, if they didn't pick whatever they stole, I would have seen it still sitting on the garage floor, and like I said, there was nothing out of place and there was nothing sitting on the floor of the garage. I would also like to add that there were no cars in the garage at the time, so i could see everything.