One day, on Miguel's fifteenth birthday, as he tends to his Abuelita's ranch, he gets a letter from his father. The letter states that Miguel will finally be crossing la linea to join him in America. The letter details the steps he'll need to take to safely cross the line.
At the beginning of Miguel's trip, on a bus that is supposed to take him a long distance north, the corrupt police stop the bus to search for illegal persons. Rather than doing their job, they take bribes to leave the people alone. It is here that Miguel discovers that his sister, Elena, has been following him on his trip. He also meets a valuable friend, Javier, on this bus.
Miguel, Javier, and Elena take a train north, but only for a while, because Javi gets hurt during a police raid. Because of this, they must find an alternative way to get north.
The trio gets lucky, because a kind person offers to take them north in their truck. It is a risky choice, but it plays out in the end. They arrive to their destination, meet up with Moises, and gear up to cross the desert leading to La Linea.
Miguel, Elena, Javi, and their leader, Moises, travel across the dangerous desert to get to La Linea. Along the way Moises gets shot by a local militia, and Javi gets lost and dies in a sandstorm. Eventually, however Elena and Miguel finally get to their destination: a city in America.
Miguel and Elena, 10 years later, are in very different places. Elena went back to San Jacinto, their hometown an started a family, and Miguel stayed in America with his parents. At the end of the day, they realized that not everything is as good as it seems, but they made the best of their situation and persevered through all of their hardships.