The Demon of the Derby: Roller derby legend Ann Calvello, now in her 70s, refuses to give up the limelight. She is still bashing heads on the banked track of any upstart league that will have her and still acting like the bawdy bad girl of the Derby, even as she bags groceries at her part-time job at Safeway. In the two years the documentary follows her, Ann simultaneously grapples with her declining ability to skate and her determination to be the first professional athlete to have competed continuously in a sport for six decades.