As the Baldwin family heads on vacation, their hometown of Los Angeles falls victim to a nuclear attack. Harry (Ray Milland), his wife, Ann (Jean Hagen), and their two teens head to their fishing retreat in the mountains, hoping to regroup and get more information. But they can't escape the frantic and irrational citizens, most of whom are dangerously deranged. Harry tries to stay calm during the nuclear-inspired end of days, but it's tempting to follow the masses' frenzied behavior.