We travel to the American southwest to what has become the most dangerous border in the world ? the one that separates the United States from Mexico. On average, one person dies per day, trying to cross illegally into the United States through the Sonoran desert. And when these illegal immigrants disappear in this deadly desert terrain, the local authorities and border patrol rarely, if ever, search for them. But, a middle-aged, former mechanic from San Diego does just that. Rafael Hernandez is known as ?The Angel in the Desert? to the many desperate families looking for loved ones who have disappeared while trying to cross into the United States. Often, it is a race against time. Dan Rather Reports airs Tuesdays at 8pm ET. "Angel of the Desert" airs Tuesday, October 18, 2011.