When Paz (Rubio) flunks her college exams, she (somewhat unwillingly) takes a job working with her father as a Madrid taxi-driver. He's part of a group of drivers called "The Family," who include a friend from Paz's childhood, Dani (Fuentes), and they begin a relationship. However, it gradually becomes apparent that the Family has a darker side. After a driver was robbed and left paralyzed, his colleagues started engaging in vigilante tactics, operating as a "death squad" and targetting junkies, homosexuals and foreigners around the city, using the anonymity afforded by their work. Dani is gradually being pulled into their circle, but when Paz realizes the truth about what's going on, she confronts her boyfriend and demands he choose between her and the Family. When this comes to the attention of the Family's leader, Calero (Lazaro), he decides Paz has become a threat that must be dealt with.
Focusing on Paz here is a big mistake, because she's a whiny teenager who does little more than Godwin Law any potentially interesting discussion the film tries to start, by yelling "Fascist!" at it. If they'd focused on Dani instead, or the Family and their motivations, it would have been more effective. Instead, left unexplored are intriguing suggestions that the Family have official backing somewhere, or an explanation of how they go from righteous indignation at a crime, to torching an immigrant camp. Obviously, Saura is operating from the basis the "vigilante justice is bad, m'kay," but this is so simple-minded in its approach as to come off feeling like an after-school special on crypto-fascist paramilitary action. The longer it goes on, the less convincing it becomes, before an ending that works only if nobody on either side of the conflict behaves with common sense. Giving Taxi Driver a political philosophy isn't enough to make this more than an annoyingly wasted opportunity.