Out of the thousands of unidentified bodies scattered across the country, many are found in South Texas, where migrants are crossing into the U.S. from Mexico.

Crossing the border is treacherous – it’s hot and there’s a lot of ground to cover. Dehydration and heatstroke claim many who try to make the trek. And dying in Brooks County means that sometimes, their bodies aren’t found, let alone identified.

So what happens to these remains? Host Al Letson and producer Delaney Hall travel to the border to find out, and they interview The Investigative Fund’s John Carlos Frey about what he learned while reporting this story.