Plot: The longest chain of mountains on the planet lies along the western edge of South America like an immense dragon - its tail falling into the freezing Antarctic Ocean, its head breathing fire 5,000 miles north. The Andes, home to the highest points outside the Himalayas, are remarkable not only for their volcanoes and their jagged peaks, the spines of the dragon's back; the niches they shelter are a world of extremes and hidden secrets