To get away with a crime, criminals look for completely untraceable guns. Enter the “ghost” gun: an exact replica with a fake serial number and no ballistic record — a gun that is potentially invisible to law enforcement.

The illegal, multibillion-dollar global sex trade includes brothels, massage parlors and online escort agencies and is one of the oldest professions. Take a look inside this illegal trade where pimps treat women as commodities — bought and sold, used and abused, then discarded.

Mexican cartels dominate an extremely lucrative industry exporting undocumented migrants and squeezing them for cash. Thousands of Central Americans head north to the US border, lured by hopes for a brighter future, but people smugglers, who are often linked to cartels, make it difficult to cross without their supervision, and for a price.

Millions of Americans love to gamble, but some forms of gambling are restricted or illegal, pushing them underground, where the rules are very different. Here, if you want to play you have to pay.

Anything and everything can be faked: watches, purses, shoes, electronics, smartphones. Go underground to see the breathtaking enterprise and expertise of counterfeiting — an economy that turns over an estimated $500 billion a year.

Knock off Pharma is on the internet, in the pharmacies and on the streets. The trade is getting ugly and the consequences are deadly.