In 2006, hedge fund manager John Paulson realized something few others suspected--that the housing market and the value of subprime mortgages were grossly inflated and headed for a major fall. Paulson's background was in mergers and acquisitions, however, and he knew little about real estate or how to wager against housing. He had spent a career as an also-ran on Wall Street. But Paulson was convinced this was his chance to make his mark. He just...