Sam Coyne is a young crewman serving aboard the Bardanos, a sand ship traversing a future desert Earth where humanity fights for survival. As a Natura—a human who reproduces and ages naturally—his existence contrasts sharply with the genetically engineered, long-lived Ideal Children who transfer consciousness. His life revolves around scavenging the wastelands aboard the Bardanos.

Sam's path shifts dramatically when he rescues Maya, a girl hunted by the militaristic Theseus Army, bringing her under Captain Bainas's protection. This act intertwines his fate with Maya's, as both seek the mythical sand whale, Ozma. Throughout this pursuit, Sam navigates rising tensions between the Natura and the Ideal Children, who see Maya as vital to their goals.

Relationships define Sam's experience on the Bardanos. He shows loyalty to Captain Bainas, who commands with an authoritative yet accessible presence. His dynamic with childhood friend Mimay adds personal stakes, though the narrative notes their relationship could have been explored further. Interactions with crewmates like Dr. Luna reinforce his place in the ship's close-knit community.

The conflict escalates into intense battles between the Bardanos and the Theseus Army, fueled by an ideological clash over humanity's future. Sam's actions directly contribute to these confrontations, placing him within larger themes of survival and resistance. While his arc engages these struggles, the narrative also indicates opportunities to deepen his personal motivations and connections, particularly concerning his bond with Captain Bainas and his quest for Ozma.