Every day, thousands attempt to enter the United States illegally from Mexico - some looking for work, some seeking a new life and others trying to smuggle drugs into the country. By foot or by car, many will do whatever it takes, often risking their lives by crossing Arizona's treacherous Sonoran Desert - "the Devil's Highway." Around the clock, the US Border Patrol scours the landscape with every means at their disposal - from stealth planes to wilderness skills - to stem the relentless human tide and protect national security. Meet the agents who patrol, the illegal immigrants who make the hazardous journey across the border and those caught up in the middle either making a profit from or offering their help to those travelling the Devil's Highway.