In a poor family in Mexico City, Adriana (Paulina Gaitán) celebrates her 13th birthday, and is happy about the bicycle her 17-year-old brother Jorge (Cesar Ramos) gives her. Their mother suspects Jorge has got the money for the present in a dishonest way, and forbids Adriana to ride it. Indeed, Jorge lures a tourist into a quiet street pretending to bring him to a prostitute, and with two friends rob the man by threatening him with guns. After the tourist complies, the three carry out a mock execution, revealing that the guns are only water guns.