How easy is it to make ricin poison? "You just get a bunch of castor beans and grind them up," says immunologist Ellen Vitetta of the University of Texas Southwestern Medical Center. Stockpiles were recently discovered in Afghan caves used by al Qaeda; Iraq is also known to have supplies. Scientists have worked for years to find a vaccine (the poison is so hard to recognize in its victims that an antidote would be impractical) but without success—until Vitetta and colleagues came upon it. The poison is best known for its role in a notorious cold war espionage murder. In...