The story opens in an impassioned meditation on memory and Mexico’s palms, volcanic table-lands and tropical flora, then narrows to the Rio Bravo frontier where a “triangular” war is played out among Americans (rangers), Mexicans (rancheros and guerrilleros) and Comanche raiders. Captain Warfield, narrator and commander of a motley corps of rangers, holds picket at an isolated pueblita. Early encounters—most notably a masked mounted pursuit—introduce Isolina de Vargas, proud, daring and beautiful, who provokes and bewitches Warfield by demanding his coveted prize, the legendary white steed of the prairies.

Tension at Don Ramon de Vargas’s hacienda thickens with ambiguous loyalties and the presence of the brutal Rafael Ijurra, later revealed as a guerrilla leader. A city masked ball deepens Warfield’s obsession; a taunting blue domino and Isolina’s caprice send him hunting the white stallion. He pursues across prairie and chaparral, is lost and rescued by veteran trappers Old Rube Rawlins and Bill Garey, kills a grizzly in close combat, and with the trappers captures the white horse. A subsequent ambush by Ijurra’s guerrillas forces a desperate defence on a mesa; Rube’s ostensible fall and comic return, lightning, and a bold nocturnal breakout plan punctuate the ordeal.

After a thunderstorm reveals enemy dispositions, a Comanche war-party routs the guerrilleros; life resumes briefly, and Warfield’s courtship of Isolina grows reciprocal amid comic relief and mounting regional instability. That peace shatters when guerrilleros later infiltrate the rancheria, inflicting savage reprisals and abducting Isolina—lashed to a white horse rigged with rockets and driven off across the plain.

Warfield’s pursuit becomes methodical man‑tracking: torchlit trail recovery, river crossings, shin‑oak forests, encounters with wild-horse drives, storms, and near‑fatal separations. He recovers two scratched messages from Isolina reporting her captivity and a resolve to die rather than submit, converting retrieval into an urgent rescue. Capturing an Indigenous scout, Warfield and his trappers disguise themselves as Comanche through paint, costume and coif and adopt a hazardous stratagem: wade the subsiding stream and creep below a turf-bank to enter the enemy bivouac unseen.

Infiltrating the camp in jaguar-skin mantle and plumed bonnet while posing as Wakono, the narrator witnesses a council to award the white mare and Isolina. The claim is awarded to a Spanish renegade, Hissoo-royo, who seizes Isolina—but she cuts her bonds with a concealed knife, mounts the white horse and flees. A chaotic pursuit follows; the narrator intervenes, stabs the renegade with a spear, and, changing horses with Rube, reaches and embraces Isolina as her horse falls mortally struck. Together they and their men cross the frontier to safety.

Allied rangers under Holingsworth and Wheatley then track and annihilate the guerrilla band; principal culprits fall and many prisoners, including Don Ramon, are liberated. The rescue resolves the central arcs—love, daring stratagem, theatrical masquerade—and closes on frontier vengeance and hard‑won reprieve.