

Except for the sap drained from opium flowers, it’s the only thing truly required to make heroin, and it doesn’t take much of the stuff to do the job. The soldiers discovered the source of the smell: acetic anhydride, a clear liquid that reeks like vinegar. In the camp’s makeshift living quarters, bags of tortilla chips and a cooler of unopened Pepsis suggested the cooks had left in haste. Five cauldrons for cooking heroin stood exposed to the sky, flaked with rust.

Behind a thicket of trees, tucked in a clearing, they found an open-air drug factory-not a huge surprise in Sinaloa, the capital of the global narcotics empire built by Joaquín “El Chapo” Guzmán. They pulled over, and a small reconnaissance team climbed out of their vehicles, then stalked down a trail. Making their way down a narrow country road in the Mexican state of Sinaloa one morning in May 2019, members of a counter-narcotics squad were struck by a strong chemical smell.
