Don Juan de Alarcón is the most dashing, quarrelsome and dissolute young man in Palencia: he has been thrown out of Valladolid, where he was sent to study, and his father, Don Gil, a devout widower plagued by gout, always ends up forgiving him. They live across the street from a convent, to the father’s delight and the son’s annoyance, as he prowls its grilles and lattices in vain. One day at Mass a young voice breaks into his daydreams: “De rodillas, caballero, que están alzando la hostia” (“On your knees, sir, they are raising the Host”). It is Margarita, the convent’s turnstile keeper.
Margarita is not yet seventeen and has spent six years shut away. Don Juan arranges to meet her at night at a chapel grille, invents a terrible secret, wars, fires and enemies closing in on Palencia, and paints a place full of parties where only he can keep her safe. Night after night the temptation grows: for the first time she makes a mirror her judge, takes off her veil and discovers that she is beautiful.
At last they agree on an escape at two in the morning, through the orchard, with a ladder. Before leaving, Margarita takes leave of the image of the Virgin whose altar she tended in a corner of the cloister, leaves its candle burning and hands it her keys: “Guárdalas: otra tornera elige a tu gusto ahora” (“Keep them: choose another keeper as you please”). What follows takes her to Madrid and the festivities of Philip IV’s court, among gambling, a dancer called Sirena and Don Gonzalo, Don Juan’s old friend.
The ending (spoilers)
Six months later the money is gone, and Don Juan, tired of Margarita, is chasing Sirena. At a supper with her, a drunken Don Gonzalo mentions Margarita and discovers that the nun is his own sister, whom he had never seen and whom his family had put in the convent to take her inheritance. They fight, and Don Juan kills him. He flees with Margarita and, after two days on the road, abandons her asleep at an inn. A gentleman and his wife take her as far as Dueñas, and she returns to Palencia to gaze, even from afar, at Don Juan’s balcony. One stormy evening she shelters in the convent church and sees a nun decking the altars, wrapped in a strange light: her name is Margarita, she is the turnstile keeper, and she has her face. It is the Virgin, who took her place while she was gone: “Yo ocupé tu lugar, piensa tú en mí” (“I took your place; keep me in your thoughts”). Margarita goes back to her cell, finds the candle still burning and the flowers still fresh, and lives in peace “sin más mundo que el torno y el altar” (“with no world but the turnstile and the altar”).