“La intrusa” tells the story of Cristián Nilsen and his younger brother Eduardo, two hardened cattle and cart drivers from the Southern orillas of Buenos Aires, a landscape inhabited by other famous Borgesian compadritos (like the Iberra brothers, who also show up here). The two Nilsens live alone, and their relationship is one of exceptional friendship and solidarity. However, this tough but ideally harmonius brotherhood is put to the test when the older brother brings Juliana Burgos, presumably a former prostitute, to live with him in the house. After a while the younger brother too falls in love with the woman, which the older notices. Eventually, Cristián offers to share Juliana sexually with Eduardo, which strengthens the latter's bond with her. Thus, the presence of the woman in their home turns the relationship between the Nilsens into one of sexual rivalry and jealousy. To end the conflict, they sell Juliana to a brothel; yet, they cannot stop desiring her, and now the two of them secretely visit Juliana there. It is then that to terminate their sexual competition, Cristián, the older, kills Juliana. In the final scene, relieved because the threat that the woman represented to their ideal friendship and brotherhood was over, the two men embrace and console each other.

The story carries an epigraph that is a laconic biblical citation: “2 Reyes, I, 26.” The reference corresponds to the Greek Bible (Septuagint), but in the traditional Hebrew Bible (after the Reformation better known in the West than the Greek Bible) that book is titled “2 Samuel.” The reference created confusion because, while the Hebrew Bible does have a book titled “2 Kings,” its first chapter does not have 26 verses, which led some readers to think that the citation was one of Borges's famous literary hoaxes. However, it is not: in the Hebrew Bible “2 Samuel, I, 26” is the verse that tells about the archetypical friendship of David and Jonathan and that, for example, in the King James Version reads, “I am distressed for thee, my brother Jonathan: very pleasant hast thou been unto me: thy love to me was wonderful, passing the love of women.” With the epigraph, as we will see, Borges alluded to the nature of the Nilsens’ exceptional friendship and the love they felt for each other.