"On every street in every city, there's a nobody who dreams of being a somebody." So went the trailer blurb for Martin Scorsese's mesmerizing "Taxi Driver," a portrait of an ordinary guy whose mind works a little differently from the rest of us. Before our eyes, Travis Bickle slides deeper and deeper into a mental abyss, into a world buffeted on all sides, as he believes, by the sordidness of the city around him--until he finally takes action.

An ex-marine, Bickle has found himself stricken with insomnia, and, in the movie's opening scene, decides to undertake driving the moonlight shift on a taxi cab simply as a way of filling up the time. Increasingly fed up with the sordid people he encounters in his midnight runs--prostitutes, pimps, pushers and various basket cases--he begins a strict physical and mental regimen in pursuit of some goal at which we can only guess. After an innocent attempt to woo a senator's aide (Cybill Shepherd) and to rescue a teenage prostitute (Jodie Foster) from the streets, Travis resorts to drastic means to make something happen. First stalking the senator, then turning his attention back to the "scum of the streets," Travis moves inexorably towards a destructive climax.

Why does he reach such a conclusion? Director Martin Scorsese does not attempt to explain, but chooses to chronicle, sometimes sympathetically, Travis's descent into violence (or, in his mind, his ascent towards justice). Whatever deeper psychological history lies in Travis's past, we never find out: as the movie's focus brings us closer and closer into his own world, we observe firsthand the wanderings of this tortured soul.

In the tradition of "the quiet guy next door," the closer we get to Travis Bickle, the less we can recognize him as normal. We see him first applying for a job as a cabbie, showing the innocent, boyish humor which will appear later in his awkward pursuit of the senator's aide Betsy, the angelic vision in white. We see him inexplicably frequenting the porn theaters of 42nd Street, then deciding in the name of cleaning things up to take up target practice and toughen his flesh via fire. Finally, he has transformed, or, more accurately, his mind has turned inside out for all to see. With a dramatically different physical appearance, Travis now packs weapons, most notably a gun he can launch from within his shirt into his right hand via a homemade spring mechanism.

The episodic format of the movie, loosely following Travis's readings from a journal he keeps, allows us to trace not only Travis's actions, but also the world he deals with so poorly. Young and charming, giving no indication of his inner turmoil, De Niro's Travis enters the senator's campaign office to proclaim with boyish impetuousness that Betsy is the most beautiful person has ever seen. Yet even here warning signs lurk, as in the way he carefully details exactly what he and Betsy have on their little coffee shop date. Travis's bizarre hypocrisy emerges when he takes Betsy to the only place of entertainment he knows in his night world: a porn shop. When Betsy leaves, Travis is puzzled, evoking the audience's pity at his inability to understand.

It is perhaps this very difficulty in processing the real world with any semblance of understanding that defines Travis's state: he cannot perceive reality beyond a basic conflict between a common man/hero in the evil world he must inhabit. Accordingly, the sight of a thirteen-year-old prostitute (Jodie Foster) fascinates him, epitomizing the destructive influence of the "scum of the streets." Later, her detestable pimp (Harvey Keitel) will be the first to face his vision of justice.

Populating this world are memorable characters, played by an excellent cast. Robert De Niro's Travis by turns charms, mesmerizes and shocks the viewer. His performance includes the now-famous monologue to the camera ("Are you talkin' to me?"), said to have been improvised. A young Jodie Foster contributes a jarring, Academy Award-winning performance as a young prostitute: one moment she is undoing a belt buckle in businesslike manner, at another she is giggly and talkative while eating a piece of bread slathered in sweetness. Harvey Keitel is the epitome of the slimy pimp--he claimed to have rehearsed with actual specimens. His wimpish bravado and bared arms give him the appearance of an evil ape. With their mindless office banter, Cybill Shepherd and Albert Brooks (playing Betsy's friend in the office) ably demonstrates the fatiguing triviality of the world. Finally, a supporting cast provides a range of characters to fit each sordid niche Travis encounters.

To illustrate the under-world of Travis's mind and daily life, Scorsese relies on these fine performances by the well-chosen cast, as well as striking camera techniques that might seem bizarre or affected if they didn't match exactly the disturbing paths of Travis's dead-end thoughts.

In one scene, Travis's cab emerges on to the screen from a Dantean burst of steam like a metallic beast as Bernard Herrman's eerie score beats to a crescendo. A close-up of Travis's wide-open eyes reflects the gaudy neon lights of 42nd Street porn shops, as he absorbs the world about him for a fare. At times, his passivity seems to reappear in his actions. Travis sees the "pow-pow" finger motion of a fellow cabbie and imitates it later--in a drastically different context, perhaps suggesting how Travis is shaped by the world around him.

Thereafter, the camera work serves to highlight both the flesh-for-money world Travis lives in and the pathetic madness of the cabbie himself. Several overhead shots of tables as hands exchange money and purchases emphasize the vacuum of this world. At several points, the camera speed is subtly slowed down, as when Travis sweeps his hand over a table in the campaign office with Betsy, making the scene even more hypnotic without our realizing it.

According to Scorsese, the key sequence in the film occurs as Travis makes a pitiful phone call to Betsy after the disastrous outing to the porn flick. The camera pans away from Travis on the phone to a shot of an empty hallway, even as he continues his largely one-sided conversation off-camera. At this point, it is as if even the subjective eye of the camera can no longer bear to watch such a pathetic scene. The harsh whiteness of the hallway's fluorescent lighting reflects the emptiness of Travis's monotonous life.

Other memorable scenes include a lingering close-up of an Alka-Seltzer being dropped into a glass. As the visual of the fiercely effervescing water and the audio of fizzing (seemingly increased in volume) fill the senses, we can feel the inwardly-turned desperation of Travis's existence, shutting out all the world in his unreasonable reason. The first two seconds of a monologue Travis delivers in another scene are later repeated; Scorcese makes it appear as if the camera is doing a double-take at Travis's tirade.

The last scenes of the film drew criticism for their violent content, and they are, indeed, bloody. Some were surprised when the film won the Palme d'Or at the Cannes Film Festival that year. But in the sudden eruption of violence in the almost dreamlike sequence, the scene almost acts like a sexual release that the earlier scenes of Travis's desperation have led to: Scorsese is merely completing the portrait.

And so as we are mesmerized as we watch this cabbie who is in turn obsessed with the "scum" around him. In Travis's words, he sees how "all the animals come out at night," and hopes that "someday a real rain will come and wash all the scum off the streets." Failing that, Travis attempts the same himself, ultimately seeking a sort of immortality, whether as an assassin of a political figure (the Senator, candidate for president) or as a noble representative of clean justice. To the very last minute of the film (when the screen changes to an eerie negative), "Taxi Driver" absorbs the audience in the madness of an ordinary man.