In a corrupt Mexican pueblo, young Mari supports her Mama and : intellectually disabled sister, Maria de los Angeles, by playing lookout for her criminal tío. Her older sister, Ally, resembles the beautiful Maria de los Angeles, but she is blessed with intellect. Tenacious Ally is investigating the connection between Mexico's organized crime and the government.

One day, Mari is caught on the job and thrown in a holding cell with other women. Ally calls and tells her someone has kidnapped Maria de los Angeles, thinking it had been Ally.

In jail, the women must huddle closely to keep warm at night. Mari meets a young, anorexic woman named Guadalupe nearing her death.

Meanwhile, Ally searches for her sister and confronts the crime boss responsible. He gives her a deal: stop her investigation in Mexico and leave for America with her mother and sisters. He offers her green cards. She agrees.

In the jailhouse, Mari and the other women cry out for Guadelupe's death. Mari is released afterwards and finds Maria de los Angeles wandering the streets. She contemplates where her Ally went.