Sand is set in a post-apocalyptic future where civilization survives in a vast desert, the ruins of the old world buried hundreds of meters beneath ever-shifting dunes. The inhabitants of two small towns, Springston and Low-Pub, scavenge ancient artifacts using specialized dive suits, technology that vibrates the sand until it flows like water, allowing divers to swim through the earth. The story follows four siblings whose lives are upended when one of them discovers a legendary buried city and uncovers a conspiracy to destroy everything they know.
Palmer, a young sand diver, hikes through the northern wastes with his friend Hap and a dozen brigands led by Brock, an imposing man whose accent no one can place. Brock has hired the divers to locate Danvar, a legendary buried city. Using an ancient map that aligns three stars with known towns, Brock has identified Danvar's likely location and excavated a shaft into the earth, held open by hundreds of wired-together dive suits. An old dive master named Yegery, one of Brock's hired experts, warns them to watch their air. Palmer learns that two previous divers attempted the descent and never returned.
Palmer and Hap descend by rope, power on their suits, and plunge into the deep sand. At roughly 250 meters, they spot massive skyscrapers perfectly preserved beneath the earth. Palmer breaks into the tallest building and finds a pocket of trapped air, landing in a conference room full of ancient artifacts. Hap follows, and the two celebrate before Hap barricades the door, steals Palmer's air tanks, and dives away, leaving Palmer stranded with no way to breathe. Hap reaches the surface and reports that Palmer did not survive. Brock confiscates the dive data, then has his second-in-command shove Hap into the shaft. Hap shatters on impact and is buried alive when Brock orders the walls collapsed.
The narrative shifts to Palmer's younger brothers. Conner, 18, and Rob, 11, live in Shantytown, a sprawl of shacks outside Springston slowly being swallowed by dunes. Their father, Farren, was once Lord of Springston but abandoned his wife and four children 12 years earlier to walk into No Man's Land, a forbidden territory to the east from which no one returns. Each year the siblings camp near the boundary to honor his memory, but Palmer has not arrived as promised. Conner, exhausted by poverty, has secretly packed supplies for a one-way journey east, planning to follow his father and never come back.
Before the trip, Conner discovers that Rob has rigged their father's old boots with wires and a homemade dive band, creating a device powerful enough to move sand without a full suit. He has the boots repaired by Graham, a family friend. That night at the campsite near the Bull's gash, a jagged crack marking the boundary of No Man's Land, Conner crosses into the forbidden territory. Almost immediately he discovers a girl crawling toward him, emaciated and near death. She recognizes Conner by name, whispers that "Father sent me" (102), and loses consciousness. Conner abandons his plan and carries her back.
The story introduces Vic, the eldest sibling and a legendary diver living in Low-Pub. Vic can reach 600 meters by staging air tanks at intervals, a secret she guards fiercely. Her boyfriend Marco, a rebel fighter, is killed when armed men burst into Graham's shop while Vic and Marco investigate Palmer's disappearance. Vic escapes with a bullet wound, pulled to safety by Graham, and sails north alone in Marco's sarfer, a wind-powered sand craft.
Meanwhile, Palmer has survived inside the buried skyscraper for days on stale air and scraps of water. He discovers ancient coins, a map of the old world, and dive tanks left by one of Brock's previous divers. The other previous diver, reduced to a feral state by starvation and isolation, attacks Palmer, who kills the man with his dive knife. Using the last tank and his failing suit, Palmer begins to ascend. At 150 meters he finds Hap's body, retrieves his regulator, and uses the remaining air to reach the surface.
Palmer stumbles upon Brock's camp while searching for food. Hiding in Brock's tent, he overhears the brigands discussing a heavy metal cylinder from a buried military site: an atomic bomb. Brock plans to destroy Springston's great wall first, then Low-Pub, intending to flatten all civilization to the south. Palmer is discovered and barely escapes. After days of desperate marching, he collapses. Vic, sailing north, spots circling crows and finds her brother face-down in the sand. She saves his life, and they sail south together.
In Springston, Conner and Rob bring the girl to their mother Rose at the Honey Hole, the brothel she owns. The girl, Violet, reveals she is their half-sister, born in a mining camp on the far side of No Man's Land. Farren has been captive there for 12 years, forced to work in mines that blast the earth with explosives. The detonations produce the thundering drums heard across the desert, and the sand burying the siblings' homeland is waste carried westward by the wind. Farren secretly built Violet a dive suit and sent her on a 12-day walk timed to the anniversary of his departure. A hidden letter warns the family not to come for him and urges them to flee west.
Vic and Palmer reach Springston just past noon. As Vic surveys the great wall, explosions detonate along its base. The wall topples, and the enormous dune stored behind it cascades through the city. Inside the Honey Hole, Conner activates his father's boots and pushes his family upward into a pocket of air. Vic uses her suit at maximum power to lift the entire buried building out of the sand, an effort that leaves her unconscious and bleeding. She recovers and spends hours with Conner pulling survivors from the ruins.
On the way to Low-Pub, Vic finds her dying friend Damien, a fellow diver, who confirms that Brock's people plan to detonate the bomb there that day. She and Conner arrive to find the town silent, bodies in the market, and Yegery standing with armed men beside the bomb's exposed sphere. Detected and disarmed, they seem trapped until Conner secretly activates his father's boots and sends columns of hardened sand through Yegery's men. A gunshot hits Conner in the shoulder, but the sphere rolls free and Vic buries it.
The family gathers at the campsite. Vic prepares to cross No Man's Land alone with the bomb, intending to destroy the civilization burying their world and to find their father. Conner argues she will never return, confessing that on the night Violet arrived, he had already crossed the gash himself and understands the lie of promising to come back. Palmer notes that Violet's accent sounds identical to Brock's, suggesting Brock may come from the same distant civilization. Vic gives Palmer the ancient map and instructions for deep diving, then says goodbye to each family member. She crosses the divide, turns back once to embrace her mother, and Rose whispers, "My sweet girl. My sweetest Victoria" (314). Vic walks east toward the thundering horizon.
On the seventh night, a blinding flash erupts in the east. The explosion silences the drumbeat of mining that has tormented the desert for generations. The family waits eight more days, but Vic does not return. On their final morning, rain falls on the desert for the first time, the moisture no longer stripped from the air by the operations Vic has destroyed. Rose falls to her knees and weeps.