On any other show, a teen dabbling in premarital sex wouldn't set off any alarms.

But when that teen is one of the Camden brood from The WB's "7th Heaven," (search) the world practically stops spinning.

"7th Heaven" — the WB's highest-rated series ever since it went on the air in 1996 — is a family drama revolving around the lives of the fairly conservative Camdens — a dad minister, his wife and their seven kids.

The show frequently has covered stories featuring everything from the right to vote and sibling rivalry to teen suicide and drug use.

Now entering its ninth season, the show will venture off into uncharted, dramatic territory: one of the Camden kids — for the first time ever — is doing the out-of-wedlock nasty. And it's going to throw the Camden clan for a loop.

Monday's season premiere episode (titled, with good reason, "Dropping Trou") several family members catch the disheveled-looking Simon (David Gallagher (search)), the Camden's middle son, and his new girlfriend, Georgia (Rheagan Wallace), in the afterglow of one of their sex sessions.

"Not in a million years did I ever think that any Camden would be having premarital sex," says the young actor who plays Simon.

"Simon is becoming a little cooler because he's catching up with a lot of issues that all my friends are dealing with or have dealt with, much more specifically," says Gallagher, a 19-year-old originally from College Point, Queens.

"All my friends that I've told, 'So on the show this year, I have sex' they're all like, 'That's awesome, finally!' "

The show has not shied away from hot-button issues like teen sex and under-age pregnancy — but until this week, those things happened only to people outside the family. The Camdens themseleves have managed to hold off on sex until after they were married — explaining in part young marriages for the three oldest kids.

Still, this being "7th Heaven" and all, don't expect anything more graphic than kissing and handholding.

"Oh Lord, no. No one's going to be dancing around in their underwear on '7th Heaven,' " says series creator and executive producer Brenda Hampton.