Mariana uncovers a supply chain of firearms being smuggled into the hands of drug cartels.

Mariana journeys into gangland to understand the violence plaguing LA.

Mariana investigates the growing popularity of bare-knuckle fighting.

Mariana investigates fentanyl, a contributor to the deadliest drug crisis in U.S. history.

Mariana retraces one of the world's most intractable smuggling routes, following cocaine's path around the world - from the Peruvian jungles, to the Colombian coastline, and to the streets of Miami.

Mariana sets off on a wild journey through California’s black market for weed, which has mushroomed since marijuana legalization four years ago.

Mariana van Zeller follows a meth superhighway from a cartel-run lab in Sinaloa across the border and into the lives of American users.

Mariana dives into the world of international scamming to understand how it all works.

Mariana meets the craftsmen who make and sell the world's finest counterfeit U.S. dollars.

Mariana attempts to understand the vanity, insecurity and greed that drives steroid use.

Mariana explores the billion-dollar underworld of illegal fishing.

Mariana van Zeller investigates underground plastic surgery, from motel-room operations to a deadly revelation about Miami’s discount surgery centers.

Mariana meets the villains behind an exploding online romance scam.

Mariana van Zeller investigates outlaw motorcycle gangs known as 1% clubs, learning about the bonds of brotherhood that fuel these violent groups.

Mariana investigates the criminals destroying the Amazon rainforest.

Mariana goes in search of the elusive chemists who make the world's LSD.

Mariana tracks a smuggling route of stolen cars from the U.S. to West Africa.

A look at the complex inner-workings of the global underworld, black and informal markets.

Mariana sets out to understand the ugly business of illicit sex in America.

Mariana exposes the dangers of the growing and deadly ghost guns industry.

Mariana explores surrogacy's dark side; a babies-for-cash black market.

Mariana investigates the lucrative black market for private data.

Mariana investigates a new breed of cocaine trafficker: lady bosses.

An alarming message from her son's middle school about MDMA sparks van Zeller into high gear. She traces the supply chain of "the love drug" within the Los Angeles clubs back to its booming epicenter in the Netherlands, where a mob-infested underworld has recently murdered a well-known journalist.

Mariana investigates how illicit oil is fueling terrorist groups worldwide.