Hear something?

I wake up in my bed, naked as the day I was born. Sudenly I hear a strange noise from outside her window. I get up, cover my breasts and lookdown at the ground below. I can't see anything. I am curious now though and so I cover my vagina with my other hand and open my bedroom door. I don't see anyone there so I walk downstairs quickly. The kitchen is dark, the lights are off and I see that the back door is open.

"Strange? I closed it just before blackjack?" I say to myself. I walk up to the door and just as I am about to close it I get a great big push from behind. It's my sister! I lose my balance and fall to the ground, uncovering for my sister to see as I do so, and see my sister laughing and closing the door. I quickly got up. My sister had locked the door from the inside!