In a scene from “Bending the Arc,” Paul Farmer reaches out to a Haitian patient. (Abramorama/Crowing Rooster Arts, Inc.)

Does the arc of the moral universe really bend toward justice, as American abolitionist Theodore Parker famously said?

It didn't look that way when Paul Farmer, a young medical student, first visited Haiti in 1983. Haiti was impoverished, racked with preventable diseases and lacking in the most basic treatment facilities.

But Farmer began to bend that arc with two friends, activist Ophelia Dahl and physician Jim Yong Kim. They started to push the international community to care about medical treatment in developing nations.

Their efforts — and their sometimes breathtaking triumphs — are the subject of a new documentary by Kief Davidson and Pedro Kos, "Bending the Arc." Using still photos, historical footage and interviews, the film follows the trio as they transform from inexperienced idealists to international health advocates.

"Bending the Arc" could give in to syrupy sentiment or overlook the actual people the trio pledged to treat, but it does not. It tells the stories of the patients. In what might be the film's most moving sequence, Kim, now president of the World Bank, breaks down when presented with old footage of a former patient — a Peruvian man who nearly died of tuberculosis — and a recent interview in which he is seen to be healthy and thriving.

There are bumps along the way. Some of the documentary's most maddening moments involve the international community's dismissal of the idea of providing better health care in under­developed nations. Officials rely on stereotypes and tired excuses to justify brushing off entire groups of people. Logistical barriers make it hard to get treatment to enough poor people.

Ultimately, though, "Bending the Arc" is not a tale of despair and death. Over three decades, Farmer's quest to treat Haitians evolved into something bigger. Partners in Health, the organization he founded with his friends, established a global framework to empower communities to treat tuberculosis, HIV/AIDS and other diseases.