The story unfolds in 1954, during the turbulent period of French Colonial Algeria as the country edges closer to its war for independence. At the center of this narrative is Daru, a French schoolteacher dedicated to educating Algerian children from surrounding villages. He spends his days teaching geography, playing with the children, and providing grain to support their families. However, the peace of his isolated schoolhouse is shattered when an acquaintance visits to warn him about the escalating tensions between the Algerian resistance and the French regime.
The next day, Balducci, a French gendarme and friend of Daru, arrives with an Arab prisoner named Mohamed. Balducci informs Daru that he is required to escort the prisoner to the nearby town of Tinguit for processing by the authorities. Despite the seriousness of the request, Daru vehemently refuses to take Mohamed, fearing that he will be sentenced to death without a fair trial, even though Mohamed has committed a grave act by killing his cousin over a dispute regarding stolen grain. Balducci, frustrated by Daru's resistance, warns him that local authorities are already suspicious of his relationship with the local populace and departs, leaving Daru with the prisoner.
After sharing a meal, Daru decides to treat Mohamed with hospitality, setting up a bed for him and tending to him when he becomes ill during the night. This act of kindness begins to bridge the gap of distrust between them. The following morning, however, Daru's newfound sense of peace is shattered when a group of men on horseback arrives, demanding that he hand over Mohamed. In a tense standoff, Daru finds himself forced to use a firearm to protect himself and Mohamed, wounding one of the attackers. Despite the immediate danger subsiding, the repercussions leave Daru and Mohamed's relationship strained.
In a moment of candidness, Daru confronts Mohamed about the chaos that transpired, expressing his anger at the situation they’ve found themselves in. Yet, after some hesitation, Mohamed asks Daru to accompany him to the authorities in Tinguit, a request that leads to a surprising change of heart for Daru, who ultimately agrees to join him on the perilous journey.
As they prepare to leave, their path becomes obstructed by a group of Frenchmen searching for a man accused of murdering cattle. The group misidentifies Mohamed as the suspect, leading to a threatening standoff that forces Daru to assert his authority by holding one of the Frenchmen at gunpoint. With tensions running high, he advises them to leave, asserting his will to protect his guest.
Finally setting out towards Tinguit, Daru and Mohamed soon find themselves pursued by Mohamed's cousins, compelling them to take a treacherous detour through the mountains. During their escape, Daru and Mohamed confront an armed man, whose decision to shoot first leads to tragic consequences. Daru fires back in self-defense, igniting a series of emotions between him and Mohamed, who finds solace in reciting prayers and burying the fallen man.
After many hours of trekking in the blistering heat, a sudden downpour drives them back to an abandoned village where they seek shelter. Here, Mohamed shares the harrowing details of his circumstances. He reveals that he killed his cousin out of desperation—his family's survival hinged on the grain, and without it, they would starve. Faced with an impending duty to pay "blood-money," he chose to surrender to the French, hoping to avert further violence against his kin.
The next day, their ordeal intensifies as they encounter members of the Algerian rebellion, who hold them captive at their base. During this time, Daru reunites with Slimane, an old friend from his military days. However, their reunion is cut short when they are informed of an approaching threat from French troops, prompting a frantic escape to a nearby cave for safety.
Inside the cave, Slimane pressures Daru to choose a side—whether against the French or among the rebels—forcing Daru to grapple with his identity. Despite his ambivalence, he and Mohamed spend the night recounting personal stories, revealing bits of their pasts, which ultimately brings them closer.
The next morning, chaos erupts as French soldiers ambush the rebels as they exit the cave. In the ensuing turmoil, many rebels are slaughtered, yet both Daru and Mohamed find themselves spared, able to convince their captors that they are merely victims in this conflict.
Resuming their journey through the desert, Daru chooses to take Mohamed to his birthplace in Berzina instead of directly to Tinguit. Along the way, Daru reveals his Spanish heritage, highlighting his feelings of alienation in Algeria. They stop at a bar, where Daru discusses hiring an escort for Mohamed before they continue their travels.
As Tinguit comes into view, Daru presents two options to Mohamed: he can surrender to the authorities. Alternatively, he could embark on a different route leading to a community of nomads who would take him in. After much contemplation, Mohamed chooses the latter path, marking a poignant farewell between the two as Daru returns to his schoolhouse, where he prepares to deliver his last lesson to the children he has come to cherish.
