Lou joins 18th Street gangsters in prison and on the street to learn why their deadly rivalry with the MS-13 is devastating El Salvador; can anyone end their war?

Ex-mafia insider Lou Ferrante visits Manila, in the Philippines, to meet one of the world's most ruthless prison gangs - the Commandos - and find out more about Manila's streets.

Lou heads to Albuquerque to meet one of the world's fastest growing prison gangs - The Burqueños. How do they recruit and are they threatening their biggest rival gang?

Lou visits Naples, a place with one of the oldest, most powerful gangs in the world - The Camorra. A number of bodies have recently been found in the city, causing world headlines.

Lou heads to Poland to infiltrate the underworld of The Grypsers. Along the way he visits some Grypser bosses, including a protected witness who is now under permanent armed guard.