The film tells the story of Rosario (Kate del Castillo), a mother who illegally immigrates to the United States, and her nine-year-old son, Carlitos (Adrián Alonso). Rosario and Carlitos have not seen each other in four years, since Carlitos was five. Rosario, now living in Los Angeles, California, calls her son (who is still in Mexico) every Sunday at 10 A.M. from a payphone. Carlitos lives in a small Mexican village with his ill grandmother and his repressive aunt and uncle, who try to take custody of him in order to get the money that Rosario sends to him. One day, while working for a woman named Carmen (Carmen Salinas), Carlitos encounters two American immigrant transporters (coyotes), Martha (America Ferrera) and David (Jesse Garcia), who offer to smuggle small children across the bor