The ads for "My Son the Fanatic" proclaim: "A new comedy from the Oscar-nominated writer of 'My Beautiful Laundrette'!" And why not? Hanif Kureishi has become a literary brand name here and in his native England. Besides, this script about a confused Pakistani taxi driver in northern England (based on Kureishi's 1994 New Yorker short story of the same name) is the most emotionally acute and potent work the writer has done for the big screen since he broke through with "Laundrette" in 1985. The newfound Islamic fundamentalism of the cabbie's son forces the cabbie to confront his midlife dissatisfactions.

The movie takes off from the hero's pivotal outburst in Kureishi's story: "I can't understand it! Everything is going from his room. I can't talk to him anymore. We were not father and son -- we were brothers! Where has he gone? Why is he torturing me?" Kureishi writes the juiciest fractured-English dialogue since Clifford Odets -- and like Odets, he has an amazing gift for slangy popular poetry. His language sweeps audiences to emotional heights by moving every viewer individually.

But the success of this wrenching funny-sad tale belongs equally to Udayan Prasad, the Indian-born, British-bred director. Under Prasad's guidance, the lead actor, Om Puri, enlarges on the story's questions. Puri's soulfulness transforms the flailing taxi driver into a gut-level liberal who refuses to accept yawning cultural gaps. And Prasad coaxes a haunting performance from Rachel Griffiths as the prostitute who befriends the cabbie, then becomes his lover. Whether Puri is making love to Griffiths or wrangling with his son, Prasad's vivid atmosphere and staging prick the imagination and pierce the heart.

When I spoke with Prasad both at the Telluride Film Festival last September and on the phone from London in June, he made it clear that "My Son the Fanatic" was as personal a project for him as it was for Kureishi. In the '80s, Prasad explored Pakistani and Anglo-Indian subjects in British TV documentaries. His debut feature, "Brothers in Trouble" (1995), employed half the core creative team of "My Son the Fanatic" -- the cinematographer, Alan Almond, the composer, Stephen Warbeck, and Om Puri -- and also centered on Pakistanis in northern England. In that volatile social melodrama (available on video), Puri imperiously, sometimes blindly, leads a band of 17 illegal aliens crammed into one house. In "My Son the Fanatic," Puri plays a vastly different figure: a bumbling, innately liberal man who at first can't face the realizations that his marriage has become stagnant and his son (Akbar Kurtha) will never find happiness with the local police chief's daughter. In both films, however, Puri strikes up a risky relationship with a white woman of ill repute. And in both films, Prasad juxtaposes urban squalor with the Pakistanis' dreams and the beauty that surrounds them in the countryside.

Making "Brothers in Trouble" helped prepare Prasad for "My Son the Fanatic," which lifts the farce and melancholy of that first feature into the realm of glorious tragicomedy. Kureishi gave birth to "My Son the Fanatic." But Prasad was uniquely qualified to be a co-parent, not a midwife.

How long have you known Hanif Kureishi?

When I first approached him I was still at the National Film School and he was writing "My Beautiful Laundrette." He was already a respected writer for the stage; I hoped there was some way we could collaborate. And I happened to know Stephen Frears, because I had worked as an editing assistant on two Alan Bennett pieces Stephen both produced and directed for TV. I remember when I met Hanif, he said he was thinking of sending "My Beautiful Laundrette" to Stephen. I said I think Frears is a fantastic choice, a great director. I take no credit for him becoming the director but I was delighted he did.

Was Frears a big influence on you as a director?

Absolutely. He taught me that you can't be precious about the material. His attitude was, "Well, we shot it, but we have to forget the experience of shooting it and look at it dispassionately and be ruthless when it comes to putting it together and not be afraid of trying things and having them fail." Actors who were coming in to do post-synchronization of dialogue responded to the way he worked with them, which was to listen to what they had to say and not impose stuff on them all the time. In the end he would make the choice but he would listen.

There's a wonderful story about Robert Mitchum at the time when he was big box office, and the producers and director of his latest film were complaining that he'd turn up, say his lines and go home. His riposte was, "You got me into this movie because you want my face. If you want my face, you have to pay me. But if you want my interest, you have to interest me." Actors are not stupid people, and if you interest them they will give you more -- they have a much better capacity to surprise you.

Stephen also taught me to collaborate with your writers. Stephen and Alan Bennett would be together all through the process. Particularly when it's someone else's original idea, it's incumbent on me to precisely understand what it is and see if I can better it, not say I want to do my thing. With Hanif on "My Son the Fanatic" the collaboration was complete.

We had kept in touch over the years. Before the story was published in the New Yorker he sent me a copy and said, "Listen, do you think there's any chance that it could be expanded into a film?" I said, "Of course there is." What excited me was the way the story looked at a global phenomenon. Fundamentalism affects every major country and religion in the world, whether with fundamentalist Christians in the United States, or fundamentalist Hindus in India. But he was depicting how it affected a really humble man -- a taxi driver, a cabbie, an ordinary guy who doesn't expect to spend too much time mulling over this particular problem.

When we first meet this character Parvez, played by Om Puri, he is a buffoon embarrassing himself in front of the people he hopes will be his son's future in-laws. Then we discover, gradually, "Hang on: He's not such a buffoon. There's much more to this character than first meets the eye." And when we first meet Rachel Griffiths' character we think she's just a prostitute. She has a client who fucks her in the back of a cab, so we have certain preconceptions about this woman. Then we realize, "Hang on: She's rather an interesting woman who happens to be a prostitute." And I love stories that allow you to go behind the fagades of the characters and see them in a different way.

You moved from India to England at age 9. Does your affection for people who feel like outsiders and yearn to belong somewhere have anything to do with your own life?

Life was much easier for me than it is for my characters. My parents were liberal, educated and aware of what was happening in the society around them; they prepared me well for the change. My interest in these characters is driven by curiosity. I actually am quite at home belonging to two cultures. A lot of people who find that there are two cultures inside of them feel as if they're lost in a limbo-land, but I'm not one of them. I love my life in England, and I love being in India when I'm in India. And having that duality enables me to enjoy the vagaries of other cultures.

What made you think that you could expand a 13-page story to feature length?

First of all, a taxi driver is constantly moving through all of society. He can pick up a rich man, a politician, a hooker. He sees the world through his rear-view mirror. So we thought, let him see the world. Hanif cleverly introduced the idea of the German businessman who hires him and is a complete hedonist -- the opposite of the fundamentalist son. That gave our character not only ideological problems but also personal and moral problems to deal with and difficult decisions to make. Of course, neither hedonism nor fundamentalism are what he wants -- he has to find his own path.

Emotionally he falls for a prostitute -- and in many sections of society going to a prostitute is not considered half as bad as falling in love with one. And I always think it's much more interesting when characters make big mistakes -- they have to decide whether it really is a mistake and whether they should try to get out of it. It's the stuff of good drama.

Along with the German businessman, you and Kureishi added a Pakistani businessman -- the cabbie's oldest friend, Fizzy.

Fizzy is the epitome of the economic migrant. He's a hard worker, he has an entrepreneurial spirit and he measures his life in material terms. He's done well: He's got himself the fanciest restaurant in town. But Fizzy is a businessman and in business it's important to keep the right people on your side and not offend certain segments of society. So when his best friend, Parvez, comes into his restaurant with a girl who is known to be a prostitute, he pushes them into a side room. There's a delicate balancing act to be played here about respect and honor, about how to treat your friends and at the same time take care of business. Fizzy has a degree of envy for Parvez. Yes, he's a taxi driver, but he has all these other interests, he's still a free spirit -- he hasn't become enslaved to materialism in the way that Fizzy has. What's unusual about Parvez as an immigrant is that material success is no longer of prime importance to him. That's why it was so crucial for us to show the audience his love for jazz and blues. He does have the need, albeit instinctive, for some spiritual and cultural connection.

When you said, "He sees the world in his rear-view mirror," it reminded me of an ad line for Scorsese's "Taxi Driver."

Of course I took a look at "Taxi Driver." As a filmmaker I strongly believe you should steal mercilessly when people far more talented and better than you have probably told your story; the trick of stealing well is to make it look as though you haven't stolen anything at all. So much of my film is set in a cab -- who better to look to than Martin Scorsese to learn how to keep the visual interest going? I don't want to make too much of the parallels between the two films, but I think "Taxi Driver" is wonderful. I love it. The point of view in it is really important -- that's what really struck a chord with me. You're in the cab with Travis, seeing the world through his eyes, so when he does outrageous things you don't lose your empathy. You don't condone what he does, but you understand it -- in your gut, not only in your head.

You and Om Puri make us feel so close to Parvez that when he tells his son that there are many ways to be a good man, we don't view it with any irony.

Well, I don't think there is any irony at that point. That's his journey, really, to arrive at that position, which is not a position he held earlier. His son is looking for a prescriptive lifestyle, which tells people how they should live their lives. But Parvez discovers that he is being dictatorial by trying to turn his son into a liberal. When he hits his son and his son asks, "Who's the fanatic now?" -- there's an acquiring of wisdom. At the end, Parvez says there are many ways to be a good man: What he's also saying to his son is, "If you want to go, go; I'm not going to stop you anymore, you live your life. But you can always come back, the door is always open."

He says to his wife, "I've done nothing wrong." But of course he's done nothing right, he's made mistake after mistake. Still, we know him so well by then that we realize nothing was maliciously intended, everything came from genuine mistakes. He was a man fumbling in the dark, to make sense of this void he found himself in, until he could eventually get his bearings.

As we negotiate life, some of us choose methods that hurt others from time to time; often the reason is that we've been hurt ourselves in the past. We're all kind of blundering along, really, and our history is important. To convey the history of a character economically in a movie is a challenge I love rising to. What's great about Hanif's script is that you could have built the story around any of the other characters, including the priest who moves into the cabbie's house and watches cartoons on TV. Hanif's characters are not cartoons, though they initially may appear to be cartoon-like.

Why don't you name the city in which the story is set?

It's not like an American film like "The Deer Hunter," where Pittsburgh is clearly identified; this city could be one of a number of northern mill towns, though it may resemble some more than others. Until the '60s and the '70s, they were the powerhouse of the British economy, centers of textile industry where lots of south Asian immigrants ended up. My city was made up of four or five places: Halifax, Bradford, Leeds, Dewsbury, Huddersfield. I looked for locations that suited the specific scenes the best.

What about the ugly scene in which the nightclub comedian racially abuses Parvez?

I think if you're going try to paint a portrait of a society you shouldn't turn away from its more unpleasant aspects. We filmed that scene in a real working-man's club. These clubs exist in all towns all over the country, but they're most closely associated with northern England. These are also places where performers do apprenticeship, or used to do before the days of television, because these are tough, demanding audiences. What was ironical is that the managers of that particular club asked the actor who played the comedian if he would like to do a real gig. Of course, the actor hated saying those racist lines.

On the other hand, you also take great pains to bring a fable-like aura to the romance between Parvez and Griffiths' prostitute; there's a fairy-tale feeling to the way she changes when she removes her wig and takes him to that glorious green patch of England outside the town.

That whole sequence is so special to me. We have to believe he can open his heart to this person. We have to see that we should be careful before condemning people for the way they make a living. And showing the old forest with the city in the distance is part of telling the story of the immigrant. I know people who have lived in Britain for 30 years or more, and all they know is the immigrant community of their town and similar immigrant communities in other towns and how to get to those and back. Apart from maybe their actual city center, and the way to the airport, they know nothing else. They've never been on a weekend holiday, they've never been to the beach and they never see the natural beauty of their country, which is on their doorstep. They've been too busy working, and then working becomes a habit, so they never see the point of not working.

When I was making documentaries, in the mid- to late-'80s, I proposed choosing six of these people and taking them on a holiday, to show them England and see how they react. These people are [originally] from rural areas, they lived on farms, but they've never been on a farm in the country they've lived in for 20 or 30 years. How extraordinary! Unfortunately the commissioning editor didn't see the potential in the story. But in this movie, with Parvez, I get to do it.