The Sonoran desert near the U.S./Mexico border

It's 114 degrees, the sun beating down relentlessly. There's no bathroom. Whatever shade you can find is going to have attracted other creatures hoping to get away from the heat and bright daylight — scorpions, coyotes, other human beings. You have only as much water as you could carry and only one change of clothes. Shoes that seemed sturdy are now torn from desert thorns. Sand is everywhere — between your toes, stuck to the sweat on your skin, ...