The year is 1969. In Oklahoma County, thunderstorms roll across an open plain, and in a remote farmhouse young Jo and her family are about to go to sleep, but her father is watching a tornado warning on TV. The TV warns that the imminent tornado may be an F5, the strongest known. Not long after the family reaches the storm cellar the huge twister hits, passing right over top of them & killing her father. 27 years later, Jo is now a storm scientist, trying to develop a tornado warning system with her soon-to-be-ex, Bill Harding. Multiple attempts fail for one reason or another, and their team sees a tremendous amount of damage & death. Then, one time, they find themselves In the damage path of a huge F5 tornado. Can they succeed in launching their test equipment, then escape the deadly storm in time?