Synthetic opioids like fentanyl accounted for around 3,000 deaths in 2013—by 2018, they accounted for over 30,000.1 Fentanyl is approximately 100 times more potent than morphine, 50 times more potent than heroin. Breathing can stop after use of just two milligrams of fentanyl. That’s about as much as trace amounts of table salt. “Ten years ago,” write the authors of a recent RAND report on the future of fentanyl, “few would have predicted that illicitly manufactured synthetic opioids from overseas would sweep through parts of Appalachia, New England, and the Midwest.” Drug epidemics and outbreaks can be surprising, taking unexpected forms at unpredictable moments in uncharacteristic patterns. But the fentanyl crisis is different. It isn’t just distressingly surprising or one more deadly drug epidemic in a grueling, tragic history of new contagions. Its magnitude, intensity, and sharp variations dwarf previous epidemics with which experts and officials are familiar, and its challenges for public health are novel and, so far, unmanageable. The recent RAND report is a comprehensive overview of the fentanyl crisis’s origins, present status, and, most disturbingly, future.