A new synthetic drug is killing more than gun crime, homicide and car accidents combined. 100 times stronger than heroin, the deadly opioid fentanyl is cheap, potent and small enough to send in the post (from China via the dark web). These market forces have seen it replacing the heroin supply, spreading unprecedented death, destruction and misery. And, like all epidemics, it is spreading fast. The death toll has disproportionately affected the homeless and marginalised. And now, due to its strength and low cost, the drug is also starting to appear in party drugs, such as cocaine and cannabis – with fatal results.