Next airing Wed May 2, 2 p.m. ET

River Under Siege

CBP Agents face the difficult challenge of defending a border drawn by the narrow, meandering course of the Rio Grande River: agents chase smugglers who risk their lives to escape high speed pursuit, track a party of migrants who claim torture at the hands of Mexican police, and thwart an unorthodox attempt to smuggle moonshine- making equipment into Mexico.