Original Story

Originally, Left 4 Dead was supposed to have a story, but the developers got rid of the idea before launch. Since the survivors are immune, the infected don't infect them, just kill them. The helicopter pilot was infected from a street pick-up, and crashes in Riverside, starting Death Toll. The boat runs out of gas and docks at Fairfield, where John and Amanda Slater become infected. The co-pilot in Dead Air went to refuel the plane, and subsequently died. Once the survivors help the pilot, he flies them to an air strip near Allegheny National Forest, where they attempt to make it to an evacuation center, where the pilot succumbs to infection. It is left unknown what happens after the Finale, but as the new Last Stand campaign was "added", something must have happened.