Houston, the fourth largest city in the US, is widely considered to be the number one hub for human trafficking in North America. The US Department of Justice estimates that at least one in five of all the country's victims are trafficked through the city, and most of these people will be forced to work in the sex industry. In Dark States - Trafficking Sex, Louis spends time with American women working in the city's illegal sex industry and explores the often complex dynamic between prostitute and pimp. He discovers a subculture that plays by rules that are morally challenging to most people and seeks to understand what stops these women breaking free. Louis also embeds with law enforcement on undercover operations and meets Vice Division officers tasked with persuading the working women to speak out against their pimps.