She romps topless in the bath with real-life Irish beau Stuart Townsend, dresses up in S&M leather and dances an erotically charged tango with on-screen lover Penelope Cruz (search).

Yes, Charlize Theron's (search) days as a "Monster" are far behind her.

After her Oscar-winning turn as splotchy-faced, overweight prostitute Aileen Wuornos (search), the South African stunner returns to full-bore glamour for the wartime romance "Head in the Clouds," which premieres at this year's Toronto Film Festival, which kicks off today.

She plays a bohemian photographer who embraces the hedonistic spirit of 1930s Paris, sharing a bed with Townsend's school teacher and Cruz's Spanish stripper.

The film features a passionate, lip-biting kiss with Cruz, a daring, up-against-the-wall oral sex scene with Townsend and an abundance of naked couplings.

But it's that steamy bath scene - in which the 29-year-old Theron appears naked but for a fedora and tie - that's really going to shock audiences.

"That scene is rather nice because when the audience first sees her, they think it will be discreetly filmed because the frame line is just above her chest," says director John Duigan.

"But just at the right moment, Charlize rises up out of the water - so it delivers, quite unselfconsciously, what the audience is hoping for.

"The tie was her idea."

Theron, who dropped 25 pounds in the month between wrapping "Monster" and starting "Clouds," initially balked at the sex scenes with Townsend, whom she's been dating since 2000.

"People say it's impossible to have [on-screen] chemistry with somebody you're in a relationship with, but in this film, it's really about destroying the relationship."

Duigan says the real-life lovers were obviously very comfortable together and brought "a genuine erotic charge" to their love scenes.

"That chemistry is very important because these are two characters who come from very different worlds and they're drawn to one another by a powerful passion," he says.

"That sense of passion needs to be - and is - palpable in the film."

Theron and Cruz - who have both trained as dancers - were equally at ease with their sexy tango scene.

"Having chosen to play these roles, they played them to the hilt - no compromise," Duigan says.

"No compromise" seems to be the motto of the 29th Toronto Film Festival (search), which also showcases same-sex smooches of Johnny Depp (search) and Liam Neeson (search), full-frontal nude scenes by Peter Sarsgaard and Neve Campbell, and Gael Garcia Bernal engaging in explicit gay sex scenes.

"Maybe something's been put in the drinking water," quips Duigan. "It's probably global warming - it's making people dress more scantily, and that's putting ideas in filmmakers' heads."

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