Fentanyl is killing at least seventy thousand Americans a year. It’s a synthetic drug, it’s up to 50 times more powerful than heroin and 100 times stronger than morphine. It’s also the biggest cause of death for Americans aged between 18 and 45: more than gun crime, more than road accidents. But where is that supply of Fentanyl to America coming from? And why are people taking it, when it’s so dangerous? And are there any solutions to this deadliest of epidemics? In today’s episode we speak to our Latin America correspondent, Guillermo Galdos, about the rare access he gained inside the Sinaloa cartel in Mexico, where he witnessed the mass production of Fentanyl. We also hear from journalist Ben Westhoff, who has spent years investigating the world of synthetic drugs in America and he explains why this crisis will get worse - even reaching the UK, before it gets better. Producer: Freya Pickford