In the opening scene, a young mother takes her crying infant outside in a stroller, only to be hit by water balloon dropped by Tomas from the rooftop of the apartment building. When Tomas' mother finds out, she decides to send him to stay with his older brother Sombra, a student in Mexico City, and Sombra's roommate Santos. After a bus ride, he arrives at his brother's home late at night. The apartment is dark without electricity. The following morning there is no breakfast. Tomas witnesses how he and his roommate can obtain electricity though the neighbor below them by communicating with a girl with Down Syndrome, who will give them an extension cord in return for a story.