Tornadoes.  They twist.  They turn.  They kill.  Husband and wife storm chasers, Jeff and Kathy Piotrowski, chase down a Missouri tornado and witness a town's devastation; Meteorologist Mark Robinson is chased by a twister in Nebraska, while a second meteorologist, Jaclyn Whittal, witnesses one of the widest tornadoes ever recorded. Experts reveal what scientists know about how tornadoes evolve and change direction, and why early detection systems are critical.