“Flowering Judas” represents a snapshot of the life of a 22-year-old American woman named Laura, who has come to Mexico to aid the Socialist cause in the aftermath of the Mexican Revolution.
As the story opens, Laura returns home to find her benefactor, Braggioni, waiting for her. Braggioni plays his guitar and sings off-key, with Laura as a reluctant audience. Braggioni pays for Laura’s room and board and regularly attempts to seduce her, forcing Laura to politely refuse him night after night. Braggioni is an embittered former revolutionary who has succumbed to materialism and prides himself on his elegant clothing and the power that he exercises in the neighborhood. Laura fears that she will become like Braggioni, cynical and compromised. Meanwhile, Laura teaches at a school for indigenous children, attends union rallies, and visits political prisoners, for whom she smuggles letters, cigarettes, and narcotics. She also furtively prays at a ramshackle Catholic church, hoping not to be seen by her comrades who would make a scandal of it.
Braggioni isn’t the only man bewitched by Laura. When she visits the nearby town of Cuernavaca, a former captain in the Zapatista army tries to teach Laura how to ride a horse (despite her already having learned how to do so in Arizona), but only succeeds in scaring the steed. A ragged minstrel, head of the Typographers Union, sings outside Laura’s house every evening until Laura’s maid, Lupe, tells her that she must throw the blossoms of the Judas tree at him to make him go away (which, unbeknownst to Laura, only leads the boy on).
Braggioni continues to enjoy his authority and manipulates two rival factions, those of the Polish agitator and the Roumanian agitator, off of each other. Braggioni shows Laura his silver ammunition belt and taunts her for her naiveté, telling her that “everything turns to dust in the hand, to gall on the tongue.” Laura feels herself to be idealistic to a fault and “not at home in the world,” and wonders if she will become like the long-suffering realist Mrs. Braggioni, who marches in picket lines and fights for the rights of the girls who work in the cigarette factory, but spends her nights crying for Braggioni, who returns from his philandering to placate her.
At the conclusion of the story, Laura is wracked with guilt over the death of a prisoner named Eugenio who overdosed on pills Laura brought to him rather than wait for Braggioni to make a deal for his release. Braggioni writes off Eugenio as a fool that they are well rid of, but to Laura he represents a martyr possessed of the purity that she has otherwise found lacking in Mexico. She goes to sleep and dreams of the ghost of Eugenio, who calls her a murderer and says he has come to take her to death. He bids her to eat the flowers of the Judas tree, then tells her that it is his body and blood. The story ends with Laura awakening and trembling, afraid to go back to sleep.