This one's a bit odd, but what if there was a magical pool house/tennis house on a family's estate. Who ever goes in is immediately attracted to the other person with them resulting in wild sex. The catch is when they leave they don't remember anything that went on in the house. So, example father and daughter go in, immediately they're turn on. After all is said and done they leave and don't remember anything. Little far fetched but it could be an interesting story.