This one happened one night in 2010. Me, my mom and older brother (who had recently moved back in because his girlfriend kicked him out) were sitting in the living room.
I believe it was somewhere between 10:00/10:30. We had one of the windows open because it was early autumn and the air outside was nice. I was sitting in a chair by the piano looking at the TV, which is in a corner with the window right next to it. This is how I saw the apparition.
Anyway, I was watching TV and suddenly something white and sort of illuminated glides by the window from right to left, in the direction of our back door. Thinking it was my mom, I didn't give it much thought. Until I realized my mom was sitting in the recliner next to me, and my brother was still on the couch. All of this processed with in about 2 seconds and so, in realizing this, I jump up and grab the baseball bat we kept next to the back door and run out to investigate.
I walked around the entire house, checking high and low only to find nothing. Keep in mind the area around the window and back door is very open and in the time of seeing it and going out, there's no way someone could have ran and hid without me at least hearing them.
Funny enough, once I go back inside, instantly my brother asked me, "Didn't find nothin', did ya?". He said this more matter of factly, than an actual question.
Come to find out he saw it too, but didn't say anything because at this point he'd been staying there about 3 weeks and had seen it twice before and had done the same thing I did.
Two nights later around the same time, I was in the kitchen making mac n' cheese when I saw it again. Only this time it was IN the house. Our stove sits right next to the doorway going into the living room and as I stood there stirring the noodles, I glanced up and saw that same figure go gliding once again from right to left, in the direction of the back door.
My little sister was curled up in the same chair that I had been in two nights prior. I walked in and decided not to say anything about it, I instead asked, "Why'd you just walk to the back door?"
She looked at me, eyes wide, and goes, "You saw that too?" Still not letting on that I knew it wasn't her I simply said, "Stop acting like it wasn't you." She then got upset and promised me that it wasn't her. I asked her what it looked like. She then described the exact same thing I'd seen.
I know it was mean to accuse her even when I knew it wasn't, but I wanted to be absolutely sure. After talking about it, we both agreed that the figure felt like a woman and meant no harm.
Later on, I learned from my brother that when he was living with his girlfriend of the time, they had seen that figure in their home. We believe that it may have followed him when he moved out.