Alien life forms have spread throughout the U.S.-Mexico border region leading to the quarantine of half of Mexico. The U.S. and Mexican militaries are battling to contain the creatures, with a wall stretching along the American border. The story follows Andrew, an American photojournalist helping his wealthy employer's daughter, Samantha, get back to America. In Mexico, Andrew buys Samantha a ferry ticket to return to America, but he gets drunk the night before they leave, and wakes up to find the tickets are stolen, so they have to travel by land through the infected zone. Their journey takes them across Central America and eventually back into the United States.
