The black market can be brutal, exploitative, corrupt. Nothing is off-limits; everything is for sale. And what you buy may not be what it seems. But it's an industry estimated to be worth hundreds of billions of dollars in the U.S. alone. Underworld, Inc. charts a global path to speak to those at the sharp end of the underworld economy. Workers, suppliers, sellers, customers, and the law enforcement officials trying to keep it in check, share their experience of a hidden world that touches us all.