We eat eels in sushi, stews, and pasta. Eels eat anything. Also they can survive outside of water for hours and live for up to 80 years. But this slippery snake of the sea harbors an even deeper mystery, one that has tormented the minds of Aristotle and Sigmund Freud and apparently the entire country of Italy: Where do they come from? We travel from the estuaries of New York to the darkest part of the ocean in search of the limits of human knowledge.