The master of documentaries Louis Theroux is back tonight with a new three-part series that explores American cities that face uniquely devastating challenges. He kicks it off tonight in Huntington, West Virginia, where he embeds himself in an Appalachian community that is being devastated and stretched to its limits by widespread heroin use. He spends time with members of the user community that are caught in the grip of drug addiction and follows the emergency services as they struggle to cope with multiple overdoses each day.