I was visiting my hometown of Del Rio, Texas, when my grandmother told me she had seen a drone flying over El Indio, a tiny village just east of the Mexican border, about 75 miles down the river. The newspapers that summer were filled with stories about the Predator drones poised to patrol the skies above the Rio Grande, but the date of deployment was not yet at hand, and in any case Predators ordinarily fly far too high to be seen from the ground, so I decided to take the afternoon to drive down to El Indio and investigate.

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1. "You Turned Around"

As a lone male in a rented minivan headed south on a remote stretch of border highway, I almost certainly fit some kind of profile. I passed several white pickups bearing the distinctive green stripe of the U.S. Border Patrol, but my first direct encounter with the authorities did not come until I pulled off the road to study with my binoculars a white speck that I had spotted high in the cloudless sky. It was not a Predator or any other UAV that I had ever seen or read about. It looked like a blimp. I put down my binoculars just as another of the green-and-white trucks pulled up. We both lowered our windows and I asked, in my best Texan, what that thing was floating up there in the sky. “It’s a weather balloon,” the officer said with a smile. I thanked him, and we both waved as I drove off, still headed south.

In El Indio, I stopped to buy a Dr Pepper and asked the old lady behind the counter, in my best Spanish, whether she knew anything about that white thing up in the sky. She did not. I decided to inquire at the post office, but it was closed. I was wondering what to do next when a minivan pulled up. I asked the driver if she knew what that white thing was up in the sky.

“It’s a satellite for the drugs,” she said. “My brother-in-law works for it.” A boy chimed in from the backseat that if I kept driving south I’d see “the building that controls it.” I thanked the woman and he...