In the backdrop of 1916, two young brothers, Hussein and Theeb, who are the second and third sons of a Bedouin sheik from the Howeitat tribe, find themselves grappling with their recent loss of parents. Growing up as part of a family devoted to guiding pilgrims, they are familiar with a life steeped in the traditions of nomadism. One fateful evening, their camp is graced by the presence of Edward, a British officer, accompanied by an Arab named Marji. In keeping with custom, a goat must be slaughtered to honor the visitors, yet Theeb, still just a boy, hesitates with this grim task. Intrigued by a wooden box that Edward carries—rumored to be filled with gold—Theeb feels an undeniable curiosity.
When Hussein is approached to lead these strangers to a Roman well situated on the pilgrims' trail, which borders a critical Ottoman railway, the brothers are warned by others in their camp about the perilous nature of the journey, citing the presence of bandits. Though Theeb longs to accompany his brother, Hussein decides it’s safer to leave him behind. However, Theeb’s determination leads him to defy his brother's wishes, and after a day’s trek, he manages to rejoin the group, despite Hussein and Marji's concerns for his safety.
Upon arrival at the well, an unpleasant surprise awaits them: the water is tainted with blood from bodies carelessly discarded nearby. Tension rises as they sense they are being observed by bandits lurking at a distance. In haste, they flee, but Edward insists on pushing forward. Unfortunately, their journey soon turns deadly; ambushed at a nearby well in the canyon, a barrage of gunfire claims Edward and Marji's lives in an instant. As chaos ensues, Hussein and Theeb seek refuge, but tragedy strikes again—Hussein meets his end in a subsequent skirmish with the raiders.
In a desperate bid for survival, Theeb tumbles into the well, where a raider cuts the rope of their water bag. The young boy finds himself alone in the vast desert, mourning for his fallen brother and digging a grave for him in the sand.
In his wanderings the following day, Theeb stumbles upon a camel approaching him with a gravely injured man atop it, who turns out to be Hassan, one of the ambushers. Initially antagonistic towards each other, the pair eventually come to the realization that cooperation is essential for survival. As Theeb tends to Hassan’s wounds, the mercenary pleads for the boy's loyalty, reminding him of their shared meal as a bond.
The next day, they manage to ride the camel towards an Ottoman rail station, encountering Arab revolutionaries who inquire about Hassan’s Western possessions, which are linked to the British officer’s plans against the Ottomans. After an unsettling passage past numerous dead revolutionaries, victims of the officer’s unfinished dealings, they arrive at the station. There, Hassan trades the officer’s belongings for silver, offering Theeb a coin in the process. But with a grim realization of Hassan’s true nature, Theeb refuses the coin, now fully aware that Hassan is profiting from the aftermath of his brother’s murder.
In a swift act of vengeance, Theeb confronts and kills Hassan, delivering his own brand of justice. As the Ottoman officer learns of Hassan's betrayal, he permits Theeb to leave. Empowered, the young boy takes hold of the camel, now able to command it, and rides off alone into the desert, an orphan seeking his own path in the harsh wilderness ahead.
