NEW YORK — Whether it wins or not, the Oscar nominee with the greatest impact — saving lives of perhaps thousands of girls — may be one you’ve never heard of.

It stars not Leonardo DiCaprio but a real-life 19-year-old Pakistani woman named Saba Qaiser. Her odyssey began when she fell in love against her family’s wishes and ran off to marry her boyfriend. Hours after the marriage, her father and uncle sweet-talked her into their car and took her to a spot along a riverbank to murder her for her defiance — an “honour killing”.

First they beat Ms Saba, then her uncle held her as her own father pointed a pistol at her head and pulled the trigger. Blood spewed, Ms Saba collapsed and her father and uncle packed her body into a large sack and threw it into the river to sink. They then drove away, thinking they had restored the family’s good name.

Incredibly, Ms Saba was unconscious but alive. She had jerked her head as the gun went off, and the bullet tore through the left side of her face but didn’t kill her. The river water revived her, and she clawed her way out of the sack and crawled onto land. She staggered toward a gasoline station, and someone called for help.

About every 90 minutes, an honour killing unfolds somewhere in the world, usually in a Muslim country. Pakistan alone has more than 1,000 a year, and the killers often go unpunished.

Watching the documentary about Ms Saba, A Girl in the River: The Price of Forgiveness, I kept thinking that just as in the 19th century the central moral challenge for the world was slavery, and in the 20th century it was totalitarianism, in this century the foremost moral issue is the abuse and oppression that is the lot of so many women and girls around the world.

I don’t know whether A Girl in the River will win an Oscar in its category, short subject documentary, but it is already making a difference. Citing the film, Prime Minister Nawaz Sharif of Pakistan has promised to change the country’s laws so as to crack down on honour killings.

Ms Saba’s story underscores how the existing law lets people literally get away with murder when honour is the excuse. After doctors saved Ms Saba’s life — as police officers guarded the door so her father didn’t return to finish the job — she was determined to prosecute her father and uncle.

“They should be shot in public in an open market,” she told the filmmaker, Ms Sharmeen Obaid-Chinoy, “so that such a thing never happens again”.

The police arrested Ms Saba’s father, Maqsood, and the uncle, Muhammad, and their defence was that they did the right thing.

“She took away our honour,” Maqsood said from his jail cell. “If you put one drop of piss in a gallon of milk, the whole thing gets destroyed. That’s what she has done. ... So I said, ‘No, I will kill you myself’.”

Maqsood said that after shooting Ms Saba he went home and told his wife, “I have gone and killed your daughter.” He added: “My wife cried. What else could she do? I am her husband. She is just my wife.”

Perpetrators of honour killings often are not prosecuted because Pakistani law allows families of victims to forgive a killing. So a man kills his daughter, the rest of the family forgives him, and he’s off the hook.

Tremendous pressure was applied to Ms Saba by community elders to pardon her father and uncle. In the end, her husband’s older brother — the head of her new family — told her to forgive and move on. “There is no other way,” he said. “We have to live in the same neighbourhood.”

Ms Saba complied, and her father and uncle were released from prison. “After this incident, everyone says I am more respected,” her father boasted. “I can proudly say that for generations to come none of my descendants will ever think of doing what Saba did.” The families still live near each other, although the father insists he will not try again to kill Ms Saba.

The way to reduce honour killings is to end the impunity. Ms Saba tried to do her part, and let’s hope Mr Sharif does indeed end the legal system of forgiveness.

“I wanted to start a national discourse about the issue,” says Ms Obaid-Chinoy, the film’s director. “Until we send people to jail and make examples of them, honour killings will continue.”

Since 9/11, the United States has spent billions of dollars reshaping Afghanistan and Pakistan with the military toolbox; I suspect we would have achieved more if we had relied to a greater extent on the education and women’s empowerment toolboxes.

A starting point would be to encourage governments to protect teenage girls from fathers who want to murder them. Chipping away at this broad pattern of gender injustice is in the interest of all of us. It is our century’s great unfinished business. NEW YORK TIMES