In the scene on the white Challenger, Bell's only support is a sturdy harness she keeps hidden under her costume. She has used rigs like this before-in her native New Zealand, doubling for Lucy Lawless on Xena, she spent entire days suspended in the air. But back then Bell was only fighting gods; here, she plays bump-and-run at 50 mph while hooked to the hood of a muscle car by a single steel cable. After almost every take, she drops her black jeans so a stunt rigger can fine-tune her "crotchless nappy"-her name for the girdle of straps and buckles that helps keep her in one piece. On-screen or off, Bell can be one of the boys-a necessary skill if you do stunts in Hollywood movies.

An insider's behind-the-scenes look into the making of Marie Claire...