Mara is a brutal gang culture in the harsh and poor Mexican countryside. Total loyalty and fidelity to the clan is required, giving many young men the only sense of belonging they have in their lives. Teenager Casper is already a tired veteran member of "Mara" when his girlfriend is killed by the violent gang leader Lil 'Mago ??as punishment for keeping his love affair secret from his gang brothers. At the same time, the teenager Sayra travels from Honduras, the long way north to try to cross the border into the United States with her father and uncle. As she makes this extremely dangerous journey balancing on the roof of a speeding train, she is attacked by Lil 'Mago ??and his gang.