Caritas Migrant House sits where the semi-arid Sahel region gives way to the Sahara Desert, on the edge of the urban sprawl of Gao, a town of more than 85,000 inhabitants in the landlocked West African nation of Mali. But as the location of Ousmane Samassékou’s unobtrusively observant “The Last Shelter,” the refuge can feel far removed from such grounded realities. With a steady stream of travelers passing briefly through, as much as the house is brick and mortar, it is also a metaphor, for a kind of mid-flight mental state. On the edge of the middle of nowhere, at the very front of the back of beyond, and only 200 miles from Timbuktu — a name still defined in English dictionaries as “the most distant place imaginable” — the Migrant House is a physical and psychological rest stop for when you’re nowhere near where you’re going, but too far gone to go back.

Samassékou’s approach, inspired by an uncle who left for Germany 32 years ago and vanished somewhere en route, is itself distant. His voice is never heard, his presence never felt, there is no scripted narration and no onscreen titling to introduce us to his subjects. It’s only incidentally that we even learn their names: Esther, a 16-year-old girl from Burkina Faso who dreams of going to Algeria with her companion, Kadi. Mariko, who has visions of a woman at his window, whom he wants to marry and bring with him to Europe. Natacha, a quiet and prayerful middle-aged woman has been at Caritas for five years — we’re never quite sure why — passing the days playing chess and dice games by herself. Even the House’s genial manager, Eric Alain Kamdem, who greets the new arrivals, advises them, helps them with forms and onward travel, cuts their hair and listens to their stories, is peripheral. In another film, his tireless work on the migrants’ behalf would be heroized.

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But here, the story is less of one man’s endeavors than of the collective comings and goings and brief encounters that happen between the House’s institutional-aqua-blue walls. Arrivals from Benin and Burkina Faso meet stranded travelers from the towns of Bamako and Bordj Badji Mokhtar. They share the bare rooms, sleeping on thin mattresses, pulling up plastic chairs into companionable knots around the TV to watch Rey Mysterio take on another WWE opponent. Sometimes they drink and chat together at night outside; other times they have informational talks that become a kind of group therapy. Those on their way out into the world are told cautionary tales by those on their way back: “Better a small job at home than to chase big delusions abroad,” says one. They mutter to each other about jihadists and the military, they draw makeshift maps in biro on scraps of paper marking the best way to avoid checkpoints and Al-Qaida strongholds.

Kamdem tries, not always successfully, to get each one to give just a single phone number of a friend or relative — many are distrustful. But a striking opening scene tells us what he needs those numbers for: The sandy ground outside Caritas is also a graveyard. The many unclaimed bodies of migrants now lie under pitiful makeshift mounds that stretch off into the distance, marked only by rusting signs bearing little more than a name and a place — Ivory Coast, Guinea, Togo. For far too many nearly anonymous people, this place of temporary respite becomes their place of permanent rest.

At times, the film’s restraint can work against it: There are so many stories we’d like to understand better but that without specific context seem a little bewildering. But when Samassékou’s diffident camera sharpens its focus a moment, it can yield a peculiar intimacy, like during the remarkable soliloquy from Esther at the end of the film. In it, she explains her reasons for deciding to continue on to Algeria, but as she never meets the camera’s eye, it feels like she is talking to herself, in an inner voice that is poetic and strange and wrenching.

And at the other end of the scale, there is a moment of grandeur. Over stark desert photography, Samassékou layers the stories of the many guests who have crossed the Sahara. At first it’s a palimpsest of voices describing the journey’s hellishness and how it can drive you mad, but it builds and builds until it’s a choral roar of anguish. Just as “The Last Shelter” has rich, soulful depths beneath a quiet surface, it suggests this human cacophony underlies the silence of the desert, part the primal scream and part the endless, ongoing lament of the migrant, who only briefly, in places like Caritas, gets to draw breath.

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