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. To begin, Stacey is on the trail of the world's most addictive and dangerous drug. Her journey takes her to Mexico, now the world's largest producer of meth, where she discovers that the battle between the cartels, the police and vigilante groups is threatening to overwhelm the very fabric of the state. She joins the army as they track down and destroy the meth super-labs that are now appearing across the country. But she learns that as soon as one lab is dismantled, others replace it. She tracks down hit men and traffickers who work for the cartels and hears shocking stories of violence from the families of their victims. It becomes clear that the power of the cartels now reaches into every corner of Mexican life and the authorities are increasingly powerless to stop it. Stacey discovers that in some places local people have become so desperate that they are taking the law into their own hands and setting up their own vigilante groups to try and fight off the cartels. With heavily-armed police, cartels and now vigilantes all squaring up against each other, Stacey reveals a country in danger of descending into chaos and disorder.

• Stacey Dooley