"Ever wish you could live your last week all over again? Well, my name's Frank B. Parker, and I do it all the time. I work for a secret government project experimenting in time travel. When things really get screwed up, I'm the guinea pig they send back to take care of it. The catch is, I can only go back 7 days."
When a neutron bomb accident obliterates all other life on Earth, Parker, Olga, Owsley, and an army officer undertake an arduous journey to reach Project Backstep and reverse things before their 7-day window of opportunity expires.
A militia leader detonates a nuclear bomb in Washington, but the Backstep goes awry when the Sphere goes back without Parker - the team has 7 days to figure out what disaster is coming and resolve it before it's too late, and all they have to help them is a reluctant psychic who was part of one of Mentnor's past experiments.