According to what Borges wrote in the epilogue of The Aleph, the plot of this story was communicated to him by his friend Cecilia Ingenieros.
[1] Emma Zunz, a worker at a textile mill, returns home and finds a letter indicating that her father has died in hospital after a Veronal overdose.
She recalls how her father told her that the textile mill owner Aaron Loewenthal was guilty of an embezzlement charge which led to his arrest, and she plots revenge.
On the following weekend, Emma calls Loewenthal, claiming she has information about an impending strike and agrees to meet him that night.
The story ends with the narrator noting that Emma’s emotions were true, only the exact circumstances, time and names were false.