The novel brings together the protagonists of the previous two books. It's 1952, and John Grady Cole, now nineteen, and Billy Parham, twenty-eight, are working together as cowboys on a small cattle ranch near Alamogordo, New Mexico, close to the border cities of El Paso and Ciudad Juárez. The ranching life they love is already dying: the army is moving to appropriate the land, and both men sense they're living at the end of something.
On a trip to a brothel in Juárez, John Grady sees a young epileptic prostitute named Magdalena and falls completely, ruinously in love with her. She is sixteen, frail, and effectively owned by Eduardo, the brothel's proprietor and pimp, who harbours his own obsessive attachment to her. John Grady resolves to marry her, and much of the novel follows his preparations: he negotiates for her freedom, restores a derelict adobe cabin in the mountains as a home for them, and arranges for her to be smuggled across the border.
Billy, older and marked by his own losses, acts as a reluctant accomplice and surrogate brother, warning John Grady throughout that the plan is doomed, while helping him anyway. His fears prove right. Eduardo has no intention of letting Magdalena go, and on the morning of her crossing she is intercepted and murdered. John Grady, learning of her death, goes to Juárez to confront Eduardo, and the two fight a prolonged knife duel in which John Grady kills the pimp but is mortally wounded himself. Billy finds him in time only to watch him die.
An epilogue leaps forward half a century. Billy, now seventy-eight and drifting homeless through a changed Southwest, shelters beneath a highway overpass where a stranger tells him a long dream-within-a-dream parable about the nature of stories, identity, and death. The novel closes with Billy taken in by a family, an old man who has outlived everyone, receiving at last a small measure of unearned kindness.
Where All the Pretty Horses was romantic and The Crossing metaphysical, Cities of the Plain is elegiac: a requiem for the cowboy world, and for the two boys the trilogy spent three books breaking.
