Part 3, "Tainted Blood," charts blood collecting following World War II. In the U.S., demand soared because of new procedures for cardiac patients and hemophiliacs, among others. But donations declined, so banks began paying donors, whose blood was more likely to be tainted with hepatitis. Then came AIDS. It found its way into the blood supply and, says narrator Kathryn Walker, "everyone was at risk." Based on commentator Douglas Starr's book "Red Gold: An Epic History of Medicine and Commerce."