Journey into the heart of the storm with this nerve-jangling British documentary on tornadoes and the thrill-seekers who risk their lives to chase the destructive funnels. Terrifying footage demonstrates the power of these awesome storms as "Twister Sisters" Melanie Metz and Peggy Willenberg race to intercept them. In the lab, scientists such as David Arnold and the University of Chicago's Ted Fujita analyze twisters and how to avoid them.