Doing my sister again

I'd really like the sex I had with my sister and of course was very willing to fuck again. She didn't break any of our father's porcelain figurines this time, we were both at home alone and bored. So, I was in a playful mood and straight asked her for a fuck, I waited for to refuse and tell me where to go but she said OKAY I bored and horny so let's fuck. So, we fucked and almost got caught on the return of our parents, that electric car doesn't make any noise. If not for the neighbor's dog, we would've caught in bed naked together. The started barking on their return and our yelled at it to shut up, thus alerting us to their return. My sister disappeared into her bedroom, and I dressed quickly and grabbed a book and pretended to be reading it. Lucky for me I had it leaning on my legs which I had my knees bent up as if it was a book rest. Because I had the book upside down, I was told we were going out to dinner at the golf club and to get ready. My sister had dressed and was likewise told to get ready to go out. My parents made a night of it at the club and me and my sister bored as we were by far the youngest there that evening. I made a promise never get caught unaware again, I installed a bell in my room activated by a motion sensor to ring when my father's car drove into the garage. It worked too well, but I turned it off and only have to turn it when I need it. Our parents were out, and I gave it a test and it worked great. Only problem my sister wasn't home to fuck, but the bell worked. The closest I've gotten to fucking my sister again was joining her shower and feeling her up. Our mother was home, and we couldn't risk anything more. But at least I know my sister is agreeable to us trying again sometime soon.