Killer comets, global tsunamis and super volcanoes might sound like the stuff of science fiction, but some people in the United States are taking such threats to the planet extremely seriously. Video journalist David Brill has been to meet the Kramer family in California, who've already bought space in an underground shelter, ready for the 'cataclysmic disaster' they believe could happen when a 'galactic alignment' takes place in 2012. He also meets shelter owner, Robert Vicino, whose website counts down the seconds to the end of the world, and offers space in his hotel-style solution to survival for tens of thousands of dollars per person. Others are approaching the future differently, believing the biggest threats we're facing are problems that we've caused ourselves. Richard Heinberg is one of the world's foremost peak oil experts, who warns that we're addicted to fossil fuels and must adapt before they run out. David takes us to a Los Angeles suburb to meet the Dervaes family of so-called 'urban homesteaders'. They've already adapted and are living self-sufficiently and almost entirely off-grid. But are they all being over cautious, or will the rest of us be under prepared?