The filmmakers waste no time throwing us into the middle of the action. We're immediately catapulted into a screeching high-speed car chase. We don't know anything about the participants, who are the good guys and who are the bad guys. All we know is that for the occupants of the car being chased, it's a life or death situation. As their pursuers zip in and out of afternoon traffic through Mexico City, guns blazing, the pursued dodge the bullets as a man in the backseat tends to an injured dog.
Blood is everywhere.
Total chaos ensues as the lead car, in an attempt to escape, barrels through a red traffic light, plowing violently into another vehicle. Glass, metal and blood spray the intersection. Iniarritu and Arriaga use the intersection as a metaphor for life in Mexico. It's here that the filmmakers bring together their three separate storylines. The characters don' t know each other, but their past, present and futures are sealed by the collision.