More than 400,000 women are part of a proposed global settlement against U.S. breast-implant manufacturers in the largest lawsuit in history. Many claim they have contracted a wide range of silicone-related diseases, but recent medical studies conducted by the nation's premier researchers have failed to find any evidence that silicone breast implants are dangerous. As Congress actively examines the powers of the FDA and the possibilities of tort reform, FRONTLINE looks at the enormous stakes involved in the clash between biomedical science and the nation's most powerful litigators.