Mr. Kalin, a close friend since they worked on “Swoon,” said of Ms. Kuras: “There’s an alertness about her, an engagement with all kinds of things. She’s not one of those people who can only talk about film. That comes across in her work. There’s a real eclectic quality to it.”  While at Brown, Ms. Kuras took photography courses at the Rhode Island School of Design and, given her interest in anthropology, found herself moving toward documentary film. Living in South Providence, among immigrants from Southeast Asia, she met refugees from Laos and learned the history of that landlocked country, the site of covert operations by the Central Intelligence Agency during the Vietnam War. After the Communist government took power in 1975, the Lao soldiers who worked for the United States became targets for persecution.  Ms. Kuras saw in her Laotian acquaintances a cruel variation on the immigrant story: a group that was not just displaced but also forgotten, unacknowledged by virtue of an association with a secret war. “I was struck that we as a country had never admitted that we had waged a war in Laos, and yet there were these people living here because of that war,” she said. “I started asking myself what happens to the people who fight our wars for us, what happens to them and their families after we leave.”  After moving to New York she decided to learn the Lao language. She found a tutor, a young man named Thavisouk Phrasavath, and realized that she had also found the subject of her film. “The moment I opened my door I knew we would be friends,” she said. Over the years the project became more collaborative. Mr. Phrasavath is credited as the co-director of “The Betrayal,” which he also edited.  The film is a poetic recounting of Mr. Phrasavath’s journey into exile, which began after his father, who had scouted bombing targets for the Americans, was sent to a re-education camp. At the age of 12 he escaped to Thailand by swimming across the Mekong River. A few years later, with his mother and seven of his nine siblings, he arrived in Brooklyn, where the family had to squeeze into a squalid apartment and contend with local gangs. The title takes on both political and personal resonance as “The Betrayal” evolves into a meditation on the failures of imperialism and of patriarchy. The film’s lengthy incubation period seems inseparable from its central themes of loss and memory.  For Ms. Kuras, who had her camera handy at several pivotal moments in the Phrasavath family saga, “The Betrayal” was never a conventional documentary. “I never thought of this a vérité project where I was observing Thavi,” she said. “The challenge as a director and cinematographer was how to make a first-person documentary without being that person.”  Speaking recently by telephone Mr. Phrasavath said: “Ellen’s a very present person. You can’t miss her when she’s around. But behind the camera it’s like she doesn’t exist.”  “The Betrayal” took so long to complete partly because Laos was a closed country for years. “I couldn’t make it work with just archival footage,” Ms. Kuras said. “We needed to show what Laos looked like.” But the process also became drawn out, she said, because there was no compulsion to finish. “I saw it as a personal project that didn’t need a definitive end.”  That changed, however, as the war in Iraq dragged on, reminding her of one of the reasons she had started “The Betrayal.” “There were parallels between Laos and what was happening in El Salvador in the ’80s,” she said. “And now there are parallels again with Iraq. It was important to finish the film now.”  Ms. Kuras is now shooting a new comedy by Sam Mendes, her first job on a feature since completing “The Betrayal,” and back in a familiar environment. “I spend most of my life on film sets,” she said.  “Finishing the film has been a melancholic experience,” she added. “But I also feel I’ve cleared the slate. In a way the film became a reference point for everything else. There’s a sense of euphoric freedom in letting it go.”  A version of this article appears in print on , on Page AR15 of the New York edition with the headline: Refugees’ Tale Took 23 Years to Tell. Order Reprints| Today's Paper|Subscribe
“The Betrayal,” a documentary about a refugee family directed by the cinematographer Ellen Kuras, stretches most definitions of a marathon shoot.