Aristotle thought they were born out of mud. A young Sigmund Freud dedicated himself to finding their testicles (spoiler alert, he failed). And a legendary Danish marine biologist spent 18 years and his wife's fortune sailing around the Atlantic Ocean in search of their birthplace. The creature that tormented all of them? It was the eel, perhaps the most mysterious fish in the world—and one of the most expensive per pound. So why are tiny, transparent, worm-like baby eels worth so much? Why have eels remained so mysterious, despite scientists' best efforts? And how has one pioneering farmer in Maine started raising eels sustainably, despite the species' endangered status? All that this episode, plus a nighttime fishing trip, suitcases full of cash, and a compelling argument that when it comes to the American Thanksgiving dinner plate, we should consider ditching the turkey—and replacing it with eel.