Lu Olkowski reports on New York's growing 'prepper' movement - people who are fearful of the future and who are preparing for the next disaster that will strike the city. They train in self-defence, plan ways to escape, store food and water in their houses and have 'bug out' bags ready at a moments notice if they have to flee. Are these people simply paranoid? Or do they have genuine concerns that all of us should take heed of?