John Glass wakes up in a desolated barn from a long cryogenic slumber to be informed that not only the planet has been devastated by a third world war, but reduced to little habitability by a subsequent alien invasion. He also learns that in order to reestablish a livable atmosphere for what's left of humanity, he'll have to go on a solitary mission to retrieve important codes dispersed in remote locations. Soon enough, he'll encounter more than he bargained for: aliens, crazy survivors, inadequate equipment, LOTS of walking and a pretty unhealthy dose of bad luck.