The screenplay — Ms. Jolie and Ms. Ung are credited as a writing team — manages the tricky task of providing enough information to push the film along while only rarely straying beyond what a child might comprehend. Loung soon discovers that she and her family, with whom she’s been forced to evacuate the capital, won’t be returning home after the promised three days. She learns that she will work in service of Angkar (the name for the Khmer Rouge leadership); surrender personal property (foreign goods, in particular, are seen as symbols of an imperialist agenda); and be separated piecemeal from her parents and siblings.

Ms. Jolie sparked an outcry for a casting process that, as recounted in a Vanity Fair interview, struck many as exploitative. The article said that Ms. Jolie was looking for children who had experienced hardship, and that for the lead role, the casting directors created a game in which children would steal money off a table and then lie when caught. (Ms. Jolie said her quotations were taken out of context; Vanity Fair stood by the story.) Whatever her process, she has found an expressive star in Ms. Sareum, who carries much of the film without words.

Whether the movie’s perspective is truly Loung’s is another matter. Ms. Jolie, working with the cinematographer Anthony Dod Mantle, shoots the character’s dream sequences in garish, supersaturated colors. The elaborate Steadicam shots and pervasive images of light streaming through foliage seem incongruously punch-drunk for a film that concerns mass starvation and death. Even a moment in which children training to fight stand completely still in a murky river during a downpour seems conceived more for its compositional possibilities than dramatic effect. Viewers familiar with the work of one of the producers, Rithy Panh, a director who has made movies about his own youth under the Khmer Rouge (including “The Missing Picture”), may find the rampant prettification poorly considered.

The most simultaneously stunning and appalling shot shows a high-angle view of Loung treading carefully through a mine-strewn forest as another woman runs through it — only to step on a mine and be killed. The moment captures everything that’s right and wrong with “First They Killed My Father”: It is gorgeous and suspenseful, and it rushes heedlessly into dangerous terrain.