She has played a repressed spinster, a bisexual bohemian and a nymphomaniac nun. But her latest role could top even that. Even if she is nothing like the fearsomely unhinged characters she regularly plays, Isabelle Huppert is quite a scary prospect. As an actor, she is dauntingly accomplished--rarely does a Cannes Film Festival go by without her. She has won the best actress award there twice (for "The Piano Teacher" in 2001, and in 1978 for "Violette Noziere"), and is a former jury member. Steve Rose speaks with Huppert.