Desperate to cure the cancer growing in her breast, Yasmary Díaz piled her three children into the back of a pickup truck and made the bone-jarring trip from her home in Guarenas to rural Zamora, up a steep and deeply rutted mountain path to a shack built of dried mud and tree branches. Here, at an altar high in the remote mountainside surrounded by mandarin trees, she sought out a shaman, a traditional healer who would call upon a powerful spirit to rid her of her disease.

According to custom, Díaz lay down on the bare dirt, surrounded by flickering candles and intricate patterns drawn in white chalk, and closed her eyes. Standing over her in a cloud of cigar smoke,