It wasn't so much a real clubhouse as a TV program, with a bunch of naked kids and a bunch of sex. It was wildly popular where it was shown, which was a long way away. All in fun, too.
A man wants to train his young babysitter to become his sex-slave. So he sets-up the babysitter to catch her masturbating and using candles to bring herself off. The man coereces her into having sex with the him so he will not have to tell her parents. She likes the sex so much that he starts training her to please him sexually and to prove that she wants to be his 'property' she must pass an all-night orgy test with multiple men.
A young innocent couple are used by the whims of their next door neighbors. The next door neighbors make it their life to scheme and get unsuspecting couples in on their little ring of swinging/swapping using any means necessary.
A disease suddenly descends on humanity. Women develop a serious illness which can only be cured by sexual intercourse, and it has to be with the right guy. No condoms, no pulling out, and he has to really want it. Bad luck? A sign from a God with most mysterious ways? Or could it possibly have been designed by a human with an agenda?