One morning in 2000, Dr. Jane Hightower walked into her surgery 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 incidents around the world. They had little in common - except a healthy appetite for certain fish. In "Diagnosis: Mercury", Dr. Hightower retraces her investigation into the modern prevalence of mercury poisoning, revealing how political calculations, dubious studies, and industry lobbyists endanger our health. While mercury is a naturally occurring element, she learns there's much that is unnatural about this poison's prevalence in our seafood.