The resulting war lasted only a few hours, but between the nuclear exchange and the years of nuclear winter that followed, the overwhelming majority of the human race was annihilated.
When the nuclear winter finally ends, the authorities send helicopters on reconnaissance missions, which reveal that against all odds, there are people still alive outside.
One family and some friends try to run away in a sailboat, and the story describes their battles with nuclear winter and fallout, and with the ensuing collapse of civilization.
