EL PASO, Texas – In a dusty lot along the U.S.-Mexico border fence, a single Border Patrol agent was stuck with few options and falling temperatures. A group of 64 parents and children had waded through a shallow bend in the Rio Grande to turn themselves in to the agent on the U.S. side. He radioed for a van driver, but there were none available. By 2 a.m., the temperature was 44 degrees. The agent handed out plastic space blankets. The group would have to wait. Mothers and fathers swaddled their families in the silvery, crinkling sheets and clustered with them on the ground, shushing the children. They shivered in the cold wind, and the sound of crying carried on, like a broken alarm.