We like to believe we're in control. But if what we're discovering about parasites is anything to go by, who is really in control is a lot more complicated, and a lot more interesting, than we ever imagined. So let "The Nature of Things with David Suzuki" help you get over the ick factor, and explore the world of parasites. So let "The Nature of Things with David Suzuki" help you get over the ick factor, and explore the world of parasites. Scientists have collected hundreds of examples of parasites that brainwash their hosts. And now researchers are starting to untangle these parasites' evolutionary tricks of the trade. In the coastal estuaries of California, Professor Kevin Lafferty of the United States Geological Survey introduces us to a flatworm that lives in three hosts - a snail, a fish and a bird. This parasite's influence is so profound that it tips the balance of the local ecosystem