Get out a bucket of cold water and lock up the children, 'cause Britney Spears (search) is in heat.

If her innocence is somehow still in question after her lesbian lip-lock with Madonna (search) on MTV, then her oversexed new album -- "In the Zone" (search) -- solves that one for good.

Men who liked to ogle her -- but have never listened to her once-sugary sound -- now have a reason to tune in: She finally sounds as hot as she looks.

No more extolling the virtues of virginity. In "Showdown," she coos, "I'm not a tease, would you undo my zipper please?"

"I was shaking my ass in the street" opens the tune "Early Mornin' " -- a sexy, growling one-night-stand regret song that should have been titled "Early Moaning."

With silky lounge grooves, hip-hop and reggae hints, and Spears' breathy vocals, it's obvious the singer is cutting her underage fans loose and trading up for a more mature and clearly more male audience.

Madonna makes a cameo on the now-familiar single, "Me Against the Music," which is good, but doesn't hint at the depth of a collection that reaches way beyond simple dance beats.

Britney accomplishes everything she wants to here. She finally separates herself from her candy-coated past and she does it with an eclectic and sophisticated pop sound.

Whether she or her producers deserve the credit, who knows -- and who cares? She is a force in contemporary entertainment and "In the Zone" reflects that.

Musically, the most interesting piece -- and the one where she sounds the most like Madonna --  is "Touch of My Hand," a dance ballad that references Asian electropop.

On the down side, Spears' vocals seem to be declining over time. On "The Hook Up," a mutant reggae/electronica tune, her voice is so processed it is unrecognizable as her.

But as we know, selling albums has less and less to do with singing -- and everything to do with image.

On past albums she's tried to be the girl next door. Now she's the one you only wish had moved next door.

"In the Zone" hits stores a week from Tuesday.