The snowy landscape in “Aga” stretches on forever, like an ocean of white. For the movie’s old man and woman, the snow is at once their backyard and their universe. They live alone with a handsome dog in a little yurt on a big plateau in an austere land where few other creatures roam. Every so often, the man climbs on a sled pulled by the dog, venturing into the unknown in what seems to be a tireless struggle for food.

There are assorted unknowns in “Aga,” which was directed by the Bulgarian filmmaker Milko Lazarov. Some of these mysteries are agreeable because they provoke questions that help give shape to an otherwise diffuse movie. It’s unclear, for instance, why the characters live alone or whether they’ve always done so. The era also seems vague. The couple lives much as they might have decades ago: They have no electricity, illuminating their yurt with only a cook fire and kerosene lamp.

Initially, Lazarov seems to be operating in the divide between documentary and fiction cinema. He narrows in on the couple’s rituals and other quotidian details, though never as much as you might like. (He shares script credit with Simeon Ventsislavov.) The relative lack of dialogue and incident, along with the unanswered questions, means that you spend a lot of time scanning the image, peering into the couple’s weathered faces, searching for clues and significance in their exchanges and their shadowy yurt.

Things happen. A jet passes way up high, and then more do. A howling storm kicks up. The woman tends a terrifying sore on her body, creating a strong, ominous sense of the inevitable. The man traps a fox and skins it. He watches a reindeer picturesquely posed in the distance. Later, he and the woman discuss reindeer and crows, and whether the seasons have changed or not. This discussion gestures toward climate change, although the characters don’t use that term. Do they know it?