Stacey Dooley returns with another hard-hitting series lifting the lid on the global war on drugs. Heading to remote and hostile regions, she investigates who's really winning this cat-and-mouse battle between the drug cartels and the police. Along the way she reveals the impact that the west's insatiable desire for more potent drugs is having on the people caught in the crossfire. Stacey travels deep into southern Africa to investigate the new and incredibly powerful strains of cannabis that are being produced and then smuggled into Britain. Travelling into the tiny state of Swaziland, Stacey meets the farmers growing stronger strains of skunk and confronts the smugglers who are getting rich shipping the drugs across the border into South Africa. Shadowing the police at Johannesburg Airport, Stacey discovers how easy it is to smuggle the drugs out of the country and into Europe - she's on the spot as customs officials uncover packets full of cannabis on their way to an address in east London. In South Africa's townships, Stacey uncovers a darker side to cannabis. Here it is being mixed with heroin and other chemicals to create nyope, a potent new cannabis cocktail that is highly addictive and is now ravaging South Africa's poorer communities.

• Stacey Dooley