In a windswept mountain pass, more than a hundred years ago, a towering Afghan man hacks a Scottish trader to death. Then the killer disappears. A British officer is determined to track him down and rides along the old Silk Route into western China. No sign of the killer but he does encounter a book of Ayurveda unearthed in the nearby desert. The Sanskrit lettering details the power of Healing Plants.

Throughout history, plants have yielded a range of medical remedies. Neem leaves so bitter they wash the worms out of stomachs in Indus Valley cities four thousand years ago. Complex Ayurveda concoctions of spices and herbs to ward off disease. Or the pills and injections of modern pharmaceuticals, a quarter of which derive from plants.

But plants are more than medicine. They have driven exploration, empires and colonization. Europe’s insatiable demand for spices and botanical remedies creates pipelines of plunder and trade across the world. As the bedrock of the pharmaceutical industry, the transformation of plants has sometimes overthrown millennia of indigenous medical wisdom.

“Healing Plants” traces the journey of plants as medicine and commodities from ancient times to the present. As you reach for that tablet in your medicine cabinet, perhaps there are echoes of its healing properties in a makeshift book found in the desert along the Silk Road.