One morning in 2000, Dr. Jane Hightower walked into her exam room to find a patient with disturbing symptoms she couldn't explain. The woman was nauseated, tired, and had difficulty concentrating, but a litany of tests revealed no apparent cause. She was not alone. Dr. Hightower saw numerous patients with similar, inexplicable ailments, and eventually learned that there were many more around the nation and the world. They had little in common--except...