In April 2011, the worst tornado outbreak in decades left a trail of destruction across the U.S., killing more than 360 people. Why was there such an extreme outbreak? How do such outbreaks form? With modern warning systems why did so many die? Is our weather getting more extreme—and if so, how bad will it get? Deadliest Tornado looks at the scientists striving to understand the forces at work behind last year's outbreak. Could their work improve tornado prediction in the future? NOVA also talks to people whose lives have been upended by these extreme weather events in an effort to learn how we all can protect ourselves and our communities for the future.