"I want to know," the old and bitter woman demanded of her young minister, "what God is saying about this."

"This" was apartheid. And to a minister, the plea was more than pertinent. Tonight at 8:30 (Channel 26) we learn how the Rev. Allan Boesak struggled to answer his angry parishioner in public television's "Choosing for Justice," a half-hour profile of the preacher-turned political activist.

His response did not come easily or quickly.

Conceived, written and directed by South African novelist Nadine Gordimer and her filmmaker son, Hugo Cassirer, the documentary was made before this year's escalation of violence altered South Africa's political landscape and before Boesak was arrested and charged with political subversion last month.

But the film's contribution lies in its exploration of how Boesak, 39, got where he is today. This theme is laid out against a backdrop of scenes of everyday South African life, offering viewers a flavor of what they would see on a casual tour of the country they have read so much about in recent news columns. Actor James Earl Jones narrates.

Boesak is a member of South Africa's "colored" population, people of mixed race who speak the language of the ruling white Afrikaners. Since the Afrikaners' great missionary zeal conflicted with their segregationist views when they converted the coloreds to their Dutch Reformed Church, they set up a separate church for them known as the Dutch Reformed Mission Church. The Reformed tradition, as the Afrikaners saw it, sanctions racial separation, and thus apartheid.

But one of their own religious sons took that idea and stood it on its head. In l982 Boesak led the initiative within the World Alliance of Reformed Churches to declare apartheid a "heresy." The Alliance of more than 70 million Christians then ejected the Afrikaners' Dutch Reformed Church from its membership and elected Boesak its first nonwhite leader.

The actions stunned the Afrikaners. Declaring apartheid a "heresy," Boesak says in the film, "takes away the moral justification of the system . . . Reformed churches are telling them, 'No, that's not what God wants.' "

Boesak, who studied in the United States for a time, springs from a long tradition of black and mixed-race clergy who have been pushed into the vanguard of opposition against apartheid by default because of the white government's refusal to allow black political organizations. This often poses moral quandaries for the clergy, who abhor violence yet see even peaceful demonstrations met with police and army units, and who must explain to a politically powerless congregation that God does care.

"My question is, as a Christian minister . . . what in the world am I supposed to do?" Boesak asks. "It would be irresponsible for me to say to people 'Let's go on demonstrating nonviolently' when I know . . . the response will be to send out the military so people can be killed.

"I am in a terrible dilemma."

Boesak was a leading force in the formation of the National Democratic Front, a multiracial coalition of antiapartheid groups that has had major political impact in the last two years. "Choosing for Justice" shows a scene of the crowd chanting for Boesak during a Cape Town meeting that launched the coalition.

"I felt scared, I must admit," Boesak says later in one of the program's most interesting moments as he recalled the meeting. "That's the kind of pressure that can be hard to resist."

By deft editing, the film offers us a two-sided recollection of a critical conversation in Boesak's development, one in which a white minister persuaded Boesak to stay in his Reformed church even though it was being used by the ruling whites to justify apartheid. That man is Beyers Naude, a Dutch Reformed minister and Afrikaner whose constant criticism of his own church caused him to be banned for seven years by the government. In separate interviews woven tightly together, Boesak and Naude recall that critical discussion.

"Allan Boesak is knocking at the doors of their consciences," Naude says of his fellow Afrikaners, "telling them 'What are you doing? And when will you be willing to do something to overcome this evil?' "

"All they need to do is say 'Here we are; we have made a mistake' . . . If only South Africa would listen," Boesak is heard saying while on the screen are two whites, backs to the camera, having cocktails on their veranda. "If a Christian people would only stop shouting their own prophets down."

Needless to say, Boesak, who could face a maximum prison term of 25 years for each of three political subversion charges, is not popular among Afrikaners. And this leads to a flaw in an otherwise good film. We don't get to hear from any of the white church leaders on the subject of Boesak.

New York-based Cassirer, 30, acknowledges the missing voice. He said one such interview was scheduled, but canceled at the last moment because of fears the government would learn of the film's production and stop it.

It's a reasonable enough fear. Although the film has already aired in six other countries and tonight's showing will make it seven, South Africans haven't yet seen "Choosing for Justice" on their televisions.

It is banned by the government.